Washington -LRB- CNN -RRB- -- The man charged in the failed Times Square bombing was working with the Taliban movement in Pakistan , the U.S. attorney general said Sunday . `` The evidence that we have now developed shows the Pakistani Taliban directed this plot , '' Attorney General Eric Holder said , describing the investigation into suspect Faisal Shahzad during an appearance on NBC 's `` Meet the Press . '' `` We know that they helped facilitate it , we know they helped direct it , and I suspect we 're going to come up with evidence that shows they helped to finance it , '' Holder said . John Brennan , the assistant to the president for counterterrorism and homeland security , told CNN 's `` State of the Union '' that the Pakistani Taliban -- also known as Tehrik-e-Taliban , or TTP -- is closely allied with al Qaeda . The group has pledged to carry out attacks outside of central Asia , including the United States , Brennan said Sunday . Shahzad has been charged in the May 1 attempted bombing in Times Square . He was arrested while trying to fly out of New York on Monday night , two days after he allegedly attempted to set off a car bomb in Times Square . The bomb failed to detonate . It was the second case in the past six months of a bungled terrorist attack in the United States , following the failed bombing of a U.S. airliner on Christmas Day . Brennan said U.S. counterterrorism efforts had degraded the ability of groups such as al Qaeda and the Taliban to launch successful attacks . `` They 're trying to find vulnerabilities in our defenses , '' Brennan said , noting the attempts have been `` unsophisticated . '' Shahzad , a Pakistani-American , had traveled to Pakistan several times in recent years , Brennan said . `` He was captured by the murderous rhetoric of al Qaeda and TTP , '' Brennan said of the suspect . Preventing attacks by individuals , especially American citizens such as Shahzad , is a `` very difficult challenge , '' Brennan said . The case raised new questions about whether terrorism suspects should be read the Miranda warning that advises them of their rights to remain silent and obtain legal representation . Critics have accused the Obama administration of losing interrogation opportunities by giving Miranda warnings to terrorism suspects , including the alleged Christmas Day airplane bomber and Shahzad . Brennan said Shahzad was interrogated for four hours under an exclusion to the Miranda warning involving public safety . Authorities then advised Shahzad of his rights , as required by law , Brennan told the `` Fox News Sunday '' program . `` It did not impede our ability to continue to acquire very important intelligence from him , '' Brennan said . `` It was , I think , a very good example that law enforcement , operating within ... the existing system , were able to leverage the opportunities that they had to get this information . '' Also on the Fox program , Republican Rep. Peter King of New York argued a change in the Miranda warning was necessary . `` If there 's another 10 , 15 , 20 plots out there , that to me is more important to get all the intelligence we can on that , '' King said . `` So I think we may have to work on revisions . '' One idea , King said , would set up `` separate system of justice dealing with American citizens who are allied with a foreign army or a foreign enemy . '' Holder also said Sunday that he was considering possible changes to the Miranda warning . Asked whether international terrorism made the current Miranda warnings too limited , Holder told the ABC program `` This Week '' that some adjustment may be necessary . The system is working so far , Holder said , but `` we also want to ... make determinations as to whether or not we have the necessary flexibility , whether we have a system that can deal with the situation that agents now confront . '' `` We 're now dealing with international terrorism , '' Holder said , adding that his department would work with Congress `` to come up with a proposal that is both constitutional , but that is also relevant to our time and the threat that we now face . ''