Washington (CNN) President Donald Trump and congressional lawmakers signaled on Tuesday that more steps need to be taken to rein in North Korea's rapidly developing nuclear program despite the United Nations Security Council's unanimous vote to pass additional sanctions on the rogue nation. 
 
 Trump noted the 15-0 UN vote during a meeting with Malaysian Prime Minister Najib Razak, but said they are "just another very small step, not a big deal" and suggested that he doesn't know "if it has any impact." 
 
 Trump added that the sanctions pale in comparison to "what ultimately will have to happen" to North Korea. 
 
 State Department spokeswoman Heather Nauert said Tuesday that the UN resolution represented "the strongest set of sanctions" so far, adding that "that's significant." Trump, she suggested, was conveying that tougher measures can still be taken because the international community is not "at the ceiling" of what can be done. 
 
 The North Korean Foreign Ministry condemned the sanctions "in the strongest terms," calling them a "heinous provocation aimed at depriving the DPRK (Democratic People's Republic of Korea, the country's official name) of its legitimate right for self-defense." 
 
 "The 'resolution' was fabricated by the US employing all sorts of despicable and vicious means and methods," the statement said, according to a report in North Korea's state-run Korean Central News Agency (KCNA). 
 
 That statement followed a similar message from Monday, in which the Ministry of Foreign Affairs reported Pyongyang would respond to any sanctions by inflicting upon the United States "the greatest pain and suffering it had ever gone through in its entire history," KCNA reported. 
 
 Frustration in the House 
 
 Trump's remarks came just hours after House lawmakers from both parties expressed frustration that the US isn't exerting greater pressure on China to stop North Korea's march toward developing nuclear weapons capable of striking the continental United States. 
 
 "We don't threaten China, even a little bit, with country sanctions because that would be difficult, politically," to do, said Rep. Brad Sherman, a California Democrat. China, North Korea's closest diplomatic ally and largest trading partner, is seen as key to solving the standoff with Pyongyang. 
 
 The committee chairman, Republican Rep. Ed Royce of California, said he agreed with Sherman and urged more sanctions against Chinese banks that do business with North Korea. "It's been a long, long time of waiting for China to comply with the sanctions we pass and, frankly, the sanctions the United Nations passes." 
 
 Meanwhile, Democrats charged that Trump is exacerbating the increasingly tense standoff with North Korea with his belligerent comments and tweets. "He talked about the response of the United States of 'fire and fury,'" said Democratic Rep. Gerald Connolly of Virginia. "Frankly, the policy looks more like fecklessness and failure." 
 
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 The lawmakers aired their frustration as US officials outlined ways in which China and Russia are failing to do everything they can to rein in North Korea, even as the nuclear threat from the rogue regime grows more intense. 
 
 China's leaders are looking the other way as DPRK uses its banking system and front companies to do business, while Russian companies continue to provide support to Pyongyang, said Marshall Billingslea, assistant secretary in the Treasury Department's Office of Terrorism and Financial Intelligence. 
 
 "It is essential that the international community work together to increase economic pressure on North Korea," Billingslea told the committee. But "DPRK bank representatives operate in Russia in flagrant disregard of the very resolutions adopted by Russia at the UN," he said in prepared remarks. 
 
 And while China accounts for 90% of North Korean exports, Billingslea said he "cannot assure the committee today that we have seen sufficient evidence of China's willingness to truly shut down North Korean revenue flows, expunge the North Korean illicit actors from its banking system, and expel the North Korean middlemen and brokers who are establishing webs of front companies." 
 
 Pressure on China 
 
 Both Billingslea and Susan Thornton, the acting assistant secretary for the State Department's Bureau of East Asian and Pacific Affairs, said that the administration is pushing China to act. "We are determined to induce the Chinese to help solve this problem," Billingslea said. 
 
 Thornton added that "we're certainly looking at every option to put pressure on China." But when asked about cutting off trade, she offered a caution. "That would be a huge step and there are lots of ramifications on that." 
 
 Secretary of State Rex Tillerson met with China's most senior diplomat, State Councilor Yang Jiechi Tuesday, where the subject undoubtedly came up. Neither official took questions from reporters during a photo op at the State Department. Meanwhile, Ambassador Joseph Yun, who serves as special representative for North Korea Policy at the State Department, is in Moscow for meetings on North Korea. 
 
 Billingslea said the US is "capable of tracking North Korea's trade on banned goods... and we will act even if China does not." He said that the US has recently caught North Korea trying to disguise the origin of ships it's using -- and added that cracking down on North Korean ship traffic will be crucial to enforcing sanctions. 
 
 These vessels have been spotted entering North Korean ports with their transponders turned off in violation of international law, Billingslea said. They have then been seen loading cargo such as coal, sailing to a Russian port where the coal is offloaded and then put on a vessel bound for China. 
 
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 Thornton said greater international cooperation in enforcing existing sanctions and applying pressure will be crucial to Tillerson's "peaceful pressure" campaign to isolate North Korea diplomatically and economically to force them to the negotiating table. 
 
 It's already yielding some successes, she said, pointing to the Philippines announcing it will cut all trade, and other countries, including Mexico and Egypt, taking steps to scale back links to Pyongyang. And she pointed to new UN sanctions, pushed through by the US. 
 
 On August 5, the US drafted a UN resolution that embargoed all imports of North Korean coal, iron, lead and seafood and required nations to cap employment of DPRK workers. On Monday, a second US-drafted UN resolution targeted North Korea's textile exports, further cut its ability to send workers overseas, curbed refined petroleum products going to Pyongyang and banned all joint ventures with it. 
 
 Tools in the toolbox 
 
 US officials have also hinted that they are ready to do more. Treasury Secretary Steven Mnuchin, speaking Tuesday at CNBC's Institutional Investor Conference Delivering Alpha, said that the US has "sent a message that anybody that wanted to trade with North Korea, we consider them not trading with us. We can put economic sanctions to stop people trading." 
 
 Citing the latest UN resolution, he said he was "very pleased with the resolution that passed. This is some of the strongest items. We now have more tools in our toolbox and we will continue to use them to put additional sanctions on North Korea until they stop this behavior." 
 
 In the meantime, Thornton said the US remains ready to counter any threat with force, even as it pushes for a diplomatic solution. 
 
 "Our military, together with our allies, remains prepared to respond immediately and resolutely to any attack or threat of attack," Thornton said. She added that "we've been clear we're not seeking regime change or collapse in North Korea, or reunification." 
 
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 "There should be no doubt about our resolve to defend our allies and our homeland," Thornton said, adding that "we are ready to respond if necessary. Meanwhile, we remain open to diplomacy, but the DPRK must show it is ready for serious engagement. We have not seen any such indication." 
 
 Indeed, the pace of North Korea's missile testing has increased dramatically. This year alone, it has conducted 16 missile tests, including two intercontinental ballistic missiles, which could reach the US. 
 
 On August 28, it launched a missile directly over Japan, endangering Japanese airspace and "and clearly was meant as a blatant threat to the people of Japan, and to us and our armed forces stationed there," said Billingslea. 
 
 And on September 3, the DPRK conducted its sixth test of a nuclear device -- the most powerful its ever detonated -- marking "an unacceptable provocation," Billingslea said. ||||| SEOUL, South Korea — The last time South Korea is known to have plotted to assassinate the North Korean leadership, nothing went as planned. 
 
 In the late 1960s, after North Korean commandoes tried to ransack the presidential palace in Seoul, South Korea secretly trained misfits plucked from prison or off the streets to sneak into North Korea and slit the throat of its leader, Kim Il-sung. When the mission was aborted, the men mutinied. 
 
 They killed their trainers and fought their way into Seoul before blowing themselves up, an episode the government concealed for decades. 
 
 Now, as Mr. Kim’s grandson, Kim Jong-un, accelerates his nuclear missile program, South Korea is again targeting the North’s leadership. A day after North Korea conducted its sixth — and by far most powerful — nuclear test this month, the South Korean defense minister, Song Young-moo, told lawmakers in Seoul that a special forces brigade defense officials described as a “decapitation unit” would be established by the end of the year. ||||| South Korea is forming a hit squad to take out North Korean leader Kim Jong Un. 
 
 Following North Korea’s successful test of its sixth and most powerful nuclear bomb earlier this month, the South Korean military has announced it’s creating an assassination unit called the Spartan 3000 to carry out night raids in North Korea. Once in the North, the group could be tasked to kill the leadership — primarily Kim. It could go in early and preempt a North Korean attack on the South, or fight in the middle of a war. 
 
 South Korean Defense Minister Song Young-moo told lawmakers of the government’s intention to build the “decapitation unit” on September 4, the day after the recent nuclear test. The administration wants the team ready by the end of the year. 
 
 The unit is central to a longstanding plan to fight North Korea if necessary — called “Korea Massive Punishment and Retaliation.” In September 2016, the North tested its fifth nuclear weapon, which at that point was the largest bomb it had detonated. Two days later, the South Korean military noted it had the option to kill North Korean leadership, including Kim. 
 
 South Korea’s previous president, the hawkish Park Geun-hye, planned to have the unit ready by 2019. But it appears the administration of the dovish Moon Jae-in wants it ready to go much sooner — likely because Moon needs to show he’s pushing back on a more aggressive North. 
 
 “I think this may be more in response to domestic pressure on the Moon administration to reintroduce US tactical nuclear weapons than an escalation with North Korea,” Troy Stangarone, an expert at the Korea Economic Institute, told me in an interview. Last week, Song floated that idea in front of political leaders, but Moon has repeatedly said he doesn’t want those weapons in South Korea. 
 
 “This has been getting quite a bit of play over the last few days, so [the administration] need[s] to be seen as taking strong steps to defend South Korea in the absence of a nuclear option,” Stangarone continued. “This is about deterrence.” 
 
 The announcement seems to have the approval of former South Korean military leaders. “The best deterrence we can have, next to having our own nukes, is to make Kim Jong Un fear for his life,” Shin Won-sik, a South Korean three-star general who retired in 2015, told the Times. 
 
 The Spartan 3000 will be a modern version of a ragtag assassination team the South Koreans created in the 1960s. Back then, the South Korean military secretly trained prisoners and others to go into North Korea and kill then-leader Kim Il Sung, Kim Jong Un’s grandfather. 
 
 But the new unit is officially recognized by the Moon government. And it’s not the only military moves this administration has made in recent days. 
 
 South Korea is preparing for an unlikely war 
 
 “We cannot rely only on our ally for our security,” Moon said in a nationally televised speech on August 15, alluding to the United States. “When it comes to matters related to the Korean Peninsula, our country has to take the initiative in resolving them.” 
 
 And take the initiative he has. On September 5, Moon told Trump that South Korea wants to build a nuclear submarine. Seoul also wants to increase the payload on its missiles so they can do more damage, and has temporarily deployed the last four THAAD missile defense systems that it bought from the US. And Moon plans to buy more military equipment from the United States now that President Donald Trump has approved the sales. 
 
 The New York Times also reports that South Korea has three ongoing war plans: “Kill Chain,” in which South Korea would preemptively launch missiles at North Korea if it detected Pyongyang was about to shoot projectiles of its own at the South; “Korea Air and Missile Defense,” which aims to take out any rockets shot by North Korea’s artillery force, which is the largest in the world; and “Korea Massive Punishment and Retaliation,” where the goal is to destroy the area in Pyongyang Kim hides in to avoid assassination. 
 
 South Korea is naturally worried about what North Korea can do. In case of a war, South Korea would be one of Pyongyang’s first targets. Seoul, South Korea’s capital with a metro area that hosts around half of the country’s 50 million people, is only about 35 miles from the inter-Korean border. That’s near where around 70 percent of North Korea’s ground forces are stationed. 
 
 One war game convened by the Atlantic back in 2005 predicted that a North Korean attack would kill 100,000 people in Seoul in the first few days alone. Others put the estimate even higher. A war game mentioned by the National Interest predicted Seoul could “be hit by over half-a-million shells in under an hour.” 
 
 Critics may still see Moon as a dove on North Korea. But that description doesn’t seem to fit after some of these latest militaristic moves — which Moon wants to do to stave off a North Korean attack.
– South Korea has taken the unusual step of publicly speaking about plans to assassinate Kim Jong Un and other North Korean leaders in the event of conflict. After North Korea's latest nuclear test, South Korean Defense Minister Song Young Moo told lawmakers that he was speeding up the creation of a "decapitation unit" capable of crossing the border for nighttime missions against North Korean facilities and its "wartime command," the New York Times reports. Officials say the special forces unit, which will apparently be comprised of members of the "Spartan 3000" unit, will be capable of striking anywhere in the Korean Peninsula within 24 hours. Song has said he wants to have the unit ready by the end of the year. The creation of the unit is part of South Korea's "Massive Punishment and Retaliation" plan for possible war with the North, Vox reports. Analysts say that by disclosing facts about the "decapitation unit," Seoul appears to want to make Pyongyang nervous enough to think twice about its nuclear program and return to the negotiating table. "The best deterrence we can have, next to having our own nukes, is to make Kim Jong Un fear for his life," says retired Gen. Shin Won Sik, formerly the South Korean military's chief strategist. President Trump, meanwhile, said Tuesday that tough new sanctions are "no big deal" compared to "what ultimately will have to happen" to North Korea, CNN reports.