Washington (CNN) -- When Times Square suspect Faisal Shahzad last traveled to Pakistan, he was looking for help from the Pakistani Taliban in carrying out a bomb attack, a senior administration official said Monday.
"The question is: Did he go there looking for help or did he fall in their lap? It seems the former. It appears he went seeking help for this attack," the official said. "He had an attack in mind when he went there."
The official spoke on the condition of anonymity because this person wasn't allowed to speak publicly about the investigation.
Top advisers to President Obama said Sunday Shahzad worked with the Taliban movement in Pakistan.
"The evidence that we have now developed shows the Pakistani Taliban directed this plot, " Attorney General Eric Holder said on NBC's "Meet the Press," describing the ongoing investigation into suspect Shahzad's actions.
State Department spokesman P.J. Crowley said Monday the Pakistani Taliban "provided him with material support that obviously helped him execute the attack."
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 on other parts of the world, including the United States, Brennan said Sunday.
Shahzad was arrested while trying to fly out of New York last Monday night, two days after federal authorities say he left a vehicle filled with explosive materials in Manhattan's Times Square. The makeshift bomb failed to detonate, preventing what could have been a deadly attack on one of the nation's busiest areas.
Shahzad, a Pakistani-American, had traveled to Pakistan several times in recent years, Brennan said.
The senior U.S. official said Shahzad received training on his most recent trip by TTP on how to execute a bomb attack. But it was unclear the extent to which the group was involved in masterminding the attack, even though Holder said Sunday, "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."
The official said that the U.S. has begun to make specific requests and recommendations to the Pakistanis to respond to the attack, which are being delivered in diplomatic, intelligence and military channels.
The official said so far the requests are related to the Shahzad investigation and involve following leads based on the information the suspect told U.S. authorities, but as the investigation progresses, the U.S. might ask the Pakistanis to do more.
Secretary of State Hillary Clinton took a tough line. On the CBS program "60 Minutes," she said, "We've made it very clear that if -- heaven forbid -- an attack like this that we can trace back to Pakistan were to have been successful, there would be very severe consequences."
CNN has learned that Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, called Gen. Ashfaq Kayani, chief of the Pakistani Army, to discuss the matter. But Mullen called to "reassure Kayani we are not trying to pressure him as a result of this case," said a senior U.S. military official. "Mullen didn't call to say, 'You gotta do more because this Pakistani-American was trained on your territory.' "