Senior White House officials said today that the Pakistani Taliban was behind the failed Times Square car bombing.
The attempt marks the first time the group has been able to launch an attack on US soil.
While US officials have downplayed the threat - citing the bomb's lack of sophistication - some feared the incident in Times Square and the Christmas Day airline bomb attempt indicated growing strength by overseas terrorist groups linked to al-Qa'ida.
The finding also raises new questions about the US relationship with Pakistan, which is widely known to have al-Qa'ida and other terrorist groups operating within its borders.
Today, suspected US missiles killed 10 people in a militant-controlled region of Pakistan close to the Afghan border, the first such strike since an alleged Pakistani-trained extremist Faisal Shahzad was accused of the Times Square attack.
US Attorney General Eric Holder said that new evidence shows that the Pakistani Taliban was "intimately involved" in the bombing plot. John Brennan, the president's homeland security and counterterrorism adviser, made similar remarks, linking the suspected bomber to the Tehrik-e-Taliban Pakistan, or TTP.
The militant group is believed to be hiding senior al-Qa'ida leaders, including Osama bin Laden.
"We know that they helped facilitate it," said Mr Holder. "We know that they probably helped finance it. And that he was working at their direction."
A US citizen of Pakistani descent, Shahzad is accused of spending five months in Pakistan before returning to the United States in February and preparing his attack.
Shahzad has told investigators that he trained in the lawless tribal areas of Waziristan, where both al-Qa'ida and the Pakistani Taliban operate. He was arrested aboard an Emirates Airlines jet in New York just minutes before it was scheduled to take off for Dubai.
After the attack, US officials said they were exploring potential links to terrorist groups overseas but cited the bomb's lack of sophistication as an indication that Shahzad was acting alone.
Last week, US Homeland Security Secretary Janet Napolitano, told NBC News that "at this point I have no information that it's anything other than a one-off".
Mr Brennan said today that the attempted bombing shows that the capability of overseas terrorist organisations is being degraded.
"They now are relegated to trying to do these unsophisticated attacks, showing that they have inept capabilities in training," he said.