WASHINGTON (CNN) -- The CIA believes extremists associated with a Pakistani tribal leader are responsible for the assassination of former Pakistani Prime Minister Benazir Bhutto, according to a U.S. intelligence official.
The official, who spoke under condition of anonymity, said the agency concluded that Baitullah Mehsud -- the leader of the Pakistani Taliban who has ties to al Qaeda -- was behind the attack.
The Pakistani government was quick to blame Mehsud's organization for Bhutto's death in December, producing an intercepted audio communication in which Mehsud confirmed his men were responsible for the attack.
The U.S. intelligence community was first cautious about drawing the same conclusion as the Pakistanis.
But after reviewing various other intelligence, the CIA agreed Mehsud played a role in Bhutto's killing, the U.S. official said.
The CIA viewpoint was first made known in a Washington Post interview with CIA Director Gen. Michael Hayden published Friday.
"This was done by that network around Baitullah Mehsud. We have no reason to question that," Hayden told the newspaper.
Mehsud operates out of the tribal areas of northwestern Pakistan. Pakistani officials have blamed Mehsud's forces for a number of attacks directed against the government, including one this week in which Islamic militants overran a military outpost in South Waziristan.
U.S. officials and terrorism experts are increasingly worried about the stability of Pakistan.
The Pakistani Taliban and al Qaeda have drawn closer ideologically over the past couple of years and see themselves at war with the Pakistani state, CNN terrorism analyst Peter Bergen said at a conference at a Washington think tank Wednesday.
He pointed to the growing number of attacks against Pakistani government officials and the ISI, the country's intelligence service.
Also at the New America Foundation conference, the organization's president, Steve Coll, indicated al Qaeda and the local insurgency are gathering strength as the government of President Pervez Musharraf is weakening.
Hayden praised Musharraf's cooperation in the war on terror, but also said the militants in Pakistan are a "serious base of danger to the current well-being of Pakistan."
A U.S. intelligence official said the stepped-up campaign by the extremists creates a "challenging environment" for the Pakistanis, but indicated the Musharraf government is "increasingly cognizant" of the problem it faces. E-mail to a friend