US attorney general Eric Holder said today evidence shows a Pakistan Taliban group closely allied with al-Qaeda was behind the attempted bombing in New York's Times Square.
In an interview on ABC's This Week, Mr Holder said there was nothing to suggest the Pakistani government was aware of the plot.
"We've now developed evidence that show the Pakistani Taliban was behind the attack," Mr Holder said. "We know that they helped facilitate it. We know that they probably helped finance it. And that he was working at their direction," he said, referring to Faisal Shahzad, the Pakistan-born naturalised American who is now under arrest.
Mr Shahzad (30), was arrested last Monday, two days after authorities say he parked a crude car bomb in Times Square. Authorities say he as been cooperating in the investigation.
Mr Holder said the Obama administration was satisfied for now with the level of cooperation it was getting from Pakistani authorities in the investigation of the attempted bombing.
In response to questions, he said the administration will have to work with Congress to see whether modifications are needed in the protections given to suspects arrested for alleged terrorist acts.
Some US politicians have suggested that people accused of terrorism should not have all the rights accorded to those charged with less serious crimes.
Mr Holder said it was important the government have the flexibility it needs to counter acts of terrorism but that any changes have to meet constitutional requirements.
On NBC's Meet the Press, Mr Holder said the administration will suggest some changes to Congress that recognize the reality that terrorism is a rising risk for the United States.
"We want to work with Congress to come up with a way in which we make our public safety exception more flexible and again more consistent with the threat we face ... This is a proposal that we're going to be making and that we want to work with Congress about," Mr Holder said.
President Barack Obama's assistant for national security, John Brennan, appearing on CNN's State of the Union, also cited Mr Shahzad's al-Qaeda link, saying evidence showed he was working with a Pakistani militant group closely allied with al-Qaeda.
"It is looking like the TTP (Pakistani Taliban) is responsible for this attempt," Mr Brennan said.
The Tehrik-e-Taliban was formed in South Waziristan and is the organization most influenced by al-Qaeda and its first leader, Baitullah Mehsud, who was killed in August 2009 by a US drone strike.
Mr Brennan said the Pakistani government's was cooperating closely with US investigators.
Meanwhile, a US drone aircraft fired two missiles into a Taliban compound in Pakistan's North Waziristan region on the Afghan border today, killing nine militants. Separately, Pakistani army helicopter gunships killed 18 militants in raids in the northwestern region of Orakzai, a government official said.
The drone attack was in Dattakhel village, about 60km west of Miranshah, the main town in North Waziristan, a hotbed for al-Qaeda and Taliban militants on the Afghan border.
Pakistan publicly objects to attacks by CIA pilotless aircraft, saying they are a violation of its sovereignty and fuel anti-US sentiment, which complicate Pakistan's efforts against militancy. Unofficially, however, analysts say Pakistan is cooperating with the United States in identifying at least some of the militant targets attacked by the drones.
Last Monday, three militants were killed in a similar strike in North Waziristan.
Fighting in recent weeks has centred in the Orakzai region where helicopters attacked four targets today.