Attorney General Eric Holder says the accused Times Square bomb plotter, Faisal Shahzad, was backed by the Pakistani Taliban.
"We've now developed evidence that shows that the Pakistani Taliban was behind the attack," Holder said in an interview on ABC News' "This Week."
"We know that they helped facilitate it," Holder added. "We know that they probably helped finance it and that he was working at their direction."
The Pakistani government, Holder said, has been "extremely aggressive" in assisting with the investigation.
"They've been cooperative with us, and I think we have been satisfied with the work that they have done," Holder said.
Former New York Mayor Rudy Giuliani, in another "This Week" interview, criticized the Obama administration for reading Shahzad his Miranda rights.
"I would not have given him Miranda warnings after just a couple of hours of questioning," Giuliani said. "I would have instead declared him an enemy combatant, asked the president to do that, and at the same time that would have given us the opportunity to question him for a much longer period of time."
Holder called for clarifying the so-called public safety exception to the requirement that Miranda rights be read to people under arrest, especially in terrorism cases.
The public safety exemption gives law enforcement agencies permission to delay protocol involving reading a suspect his or her rights when the suspect is believed to be a significant threat to the general public.
"We're now dealing with international terrorism," Holder said, "and if we are going to have a system that is capable of dealing in a public safety context with this new threat, I think we have to give serious consideration to at least modifying that public safety exception."
Holder said the administration will be working with Congress to modify the exception in a way that "gives the necessary clarity, is flexible, but is also constitutional."
Shahzad, a 30-year old naturalized U.S. citizen from Pakistan, was arrested Monday night at New York's JFK Airport as he attempted to leave the country on a Dubai-bound Emirates airline flight.
Holder also addressed the question of where the trial of accused 9/11 mastermind Khalid Sheikh Mohammed will be held. Although the Obama administration pulled back Holder's decision last year to hold the trial in Manhattan, Holder left open the possibility that a New York trial still could happen.
"Nothing is really off the table," Holder said.
He pushed back on a suggestion that the White House has politicized the matter.
"I don't think the decision has been politicized at all," he said. "This is a national security matter, and I think it's appropriate for the president to be involved in that decision."
On the subject of Arizona's controversial new immigration law, Holder said he didn't believe it had "racist in motivation" but he still expressed concern the law could lead to racial profiling.
He is concerned about how the law "will be perceived and how it perhaps could be enacted, how it could be carried out. I think we could potentially get on a slippery slope where people will be picked on because of how they look as opposed to what they have done, and that is, I think, something that we have to try to avoid at all costs."
Immigration, Holder said, is a national problem and a "state-by-state solution to it is not the way in which we ought to go."