-LRB- CNN -RRB- -- Stocks on key Asian exchanges dropped modestly early Monday on what is likely to be an eventful day in world markets , following Standard and Poor 's downgrade of the U.S. credit rating . In early Tokyo trading , the Nikkei index fell 124 points , or 1.3 % . South Korea 's KOSPI index slipped 1.6 % . In Australia , the All Ordinaries index lost 0.7 % . The Shanghai composite started 0.8 % lower . Hong Kong 's Hang Seng index tumbled 2.6 % at the open . Similarly , U.S. stock futures fell around 1.7 % in early electronic trading Sunday . The futures were the first U.S. gauge of investor sentiment following Friday night 's downgrade , removing the United States ' AAA status for the first time . They give an indication of how investors will react when regular-hours U.S. trading begins at 9:30 a.m. ET Monday . Besides the U.S. downgrade , investors are concerned about the debt crisis in some European nations , though actions on the part of the G7 and the European Central Bank Sunday helped to allay some of those fears . Financial representatives of leading industrial nations said they are committed to taking `` all necessary measures to support financial stability and growth in a spirit of close cooperation and confidence . '' They welcomed the `` decisive actions taken in the U.S. and Europe '' and `` the additional policy measures announced by Italy and Spain to strengthen fiscal discipline and underpin the recovery in economic activity and job creation . '' `` We are committed to taking coordinated action where needed , to ensuring liquidity , and to supporting financial market functioning , financial stability and economic growth , '' G7 finance ministers and central bank governors said in a Sunday night statement . Treasury Secretary Tim Geithner had been expected to take part in a conference call with representatives of the other G7 nations to discuss the downgraded U.S. credit rating , a G7 official told CNN . The G7 nations are the United Kingdom , France , Germany , Italy , Japan , Canada and the United States . Similarly , the European Central Bank made a bid to calm markets Sunday . It said it would implement a bond-purchase program and welcomed announcements by Italy and Spain on new measures meant to reduce their deficits . It told the governments of those countries that a `` decisive and swift implementation '' of reforms is `` essential . '' The move represents an escalation in the official response to Europe 's debt crisis , which is now more than a year old and until recently was contained to smaller economies like Greece , Ireland and Portugal . International Monetary Fund Managing Director Christine Lagarde cheered the announcements . `` I welcome the statements from the European Central Bank , from the leaders of Germany and France as well as from the G7 , and their renewed commitment to take all necessary action in a coordinated way to ensure stability and liquidity in the financial markets . This cooperation will contribute to maintaining confidence and spurring global economic growth , '' she said in a statement . Middle Eastern markets , the first to open since the downgrade , were sharply lower on Sunday . Israel 's market temporarily halted trading at one point and finished down more than 6 % , while the Dubai Financial Market General Index fell 3.7 % . The General Index on the Abu Dhabi Securities Exchange was down more than 2.5 % , while in Saudi Arabia , the Tadawul All-Share Index dropped nearly 5.5 % in trading Saturday . U.S. officials are talking to a `` wide range of investors '' about the downgrade by the credit agency to try to `` mitigate '' any short-term negative impact from Friday 's announcement , a Treasury official told CNN . Top Standard & Poor 's officials said Sunday that the downgraded credit rating for the United States was both a call for political consensus on significant deficit reduction and a warning of possible further credit problems down the road . `` We have a negative outlook on the rating and that means that we think the risks currently on the rating are to the downside , '' said David Beers , the S&P global head of sovereign ratings , on `` Fox News Sunday . '' However , Beers said markets were reacting to the debt crises in some European countries and fears of a global economic slump , rather than the U.S. credit downgrade alone . John Chambers , the S&P head of sovereign ratings , told ABC 's `` This Week '' program Saturday that it could take years for the United States to return to AAA status . `` Well , if history is a guide , it could take a while , '' Chambers said . `` We 've had five governments that lost their AAA that got it back . The amount of time that it took for those five range from nine years to 18 years , so it takes a while . '' The agency 's concerns `` are centered on the political side and on the fiscal side , '' Chambers said . `` So it would take a stabilization of the debt as a share of the economy and eventual decline , '' he said . `` And it would take , I think , more ability to reach consensus in Washington than what we 're observing now . '' Both Beers and Bill Miller , chairman and chief investment officer at Legg Mason Capital Management , told the Fox program that they do n't expect the U.S. downgrade to cause a spike in interest rates , one of the possible results of the higher risk now attached to U.S. debt . `` I do n't think we 'll pay more in interest , '' Miller said , calling the downgrade more of a symbolic event than an economic event . However , he warned of continuing market volatility in coming days driven by uncertainty . Rating agencies such as S&P , Moody 's and Fitch analyze risk and give debt a grade that is supposed to reflect the borrower 's ability to repay its loans . The safest bets are stamped AAA . That 's where the U.S. debt has stood for years . Moody 's first assigned the United States an AAA rating in 1917 . Fitch and Moody 's , the other two main credit ratings agencies , maintained the AAA rating for the United States after last week 's debt deal , though Moody 's lowered its outlook on U.S. debt to `` negative . '' A negative outlook indicates the possibility that Moody 's could downgrade the country 's sovereign credit rating within a year or two . U.S. Treasury officials received S&P 's analysis Friday afternoon and alerted the agency to an error that inflated U.S. deficits by $ 2 trillion , said an administration official , who was not authorized to speak for attribution . The agency acknowledged the mistake , but said it was sticking with its decision . The administration official called it `` a facts-be-damned decision ... Their analysis was way off , but they would n't budge . '' Saturday , Gene Sperling , director of Obama 's National Economic Council , criticized S&P 's call . `` The magnitude of their error and the amateurism it displayed , combined with their willingness to simply change on the spot their lead rationale in their press release once the error was pointed out , was breathtaking . It smacked of an institution starting with a conclusion and shaping any arguments to fit it , '' he said . But Beers defended his agency 's move on Sunday , telling the Fox program : `` The underlying debt burden of the U.S. government is rising and will continue to rise over the next decade . '' CNN 's Tom Cohen , Kyung Lah and Mark Meinero contributed to this report .