The CIA has concluded that a Pakistani tribal leader's network was behind the assassination of former Pakistan Prime Minister Benazir Bhutto, according to a U.S. intelligence official.

The tribal leader, Baitullah Mehsud, is an extremist with strong ties to Al Qaeda and an alliance with Taliban. He heads up a network in South Waziristan, a lawless border region abutting Afghanistan. He has been blamed for an organized campaign of assassinations of Pakistani officials and homicide bombings in the country.

The Central Intelligence Agency concluded that Mehsud was behind the Dec. 27 killing of Bhutto shortly after it occurred, according to an intelligence official who spoke on condition of anonymity because of the sensitivity of the matter.

The Washington Post first reported the CIA's conclusion on Friday, in an interview with CIA director Michael Hayden. "This was done by that network around Baitullah Mehsud. We have no reason to question that," Hayden told the newspaper.

The intelligence official said Mehsud, believed to be in his early 30s, is a "committed jihadist" who recruits and trains homicide operatives for the Taliban and Al Qaeda. His network carries out homicide attacks in Pakistan and Afghanistan, primarily along the border. The attacks have stretched from Nuristan province in northeast Afghanistan to Helmand province in the south.

He has bragged of having 3,000 would-be homicide bombers. His homicide squads have taken credit for attacks against the military and police in northwestern Pakistan, as well as bombings at a hotel in the capital of Islamabad that killed a security guard and at the Islamabad international airport.

Mehsud's men kidnapped nearly 250 Pakistani soldiers in August and held them until November, when he negotiated the release of two dozen jailed tribesmen, a group that included extremists and would-be homicide bombers.

Mehsud's forces are believed to be behind an attack Wednesday on a Pakistani army fort near the Afghan border that left at least 22 soldiers dead or missing. The insurgents later abandoned the fort.

Pakistani President Pervez Musharraf has blamed Mehsud's movement, Tehrik-e-Taliban, for 19 homicide attacks that killed more than 450 people over the last three months.

Mehsud, whose tribe of the same name is the most violent in South Waziristan province, signed a peace pact with Pakistan's army in February 2005. In it, he promised to deny shelter to foreign Al Qaeda fighters in exchange for an end to military operations in the region and compensation for tribesmen killed by the military.

"It was a disaster for the U.S. The bad guys had more operational freedom," said Rep. Mike Rogers, the senior Republican on the House Intelligence subcommittee on terrorism. Rogers has made more than a dozen trips to Pakistan and Afghanistan in the last two years.

Al Qaeda has since reestablished its headquarters in the sanctuary of the tribal area, and homicide bombers and Taliban fighters are believed to cross into Afghanistan regularly to attack civilians and U.S. and Afghan forces.

Mehsud fought in the late 1990s for the Taliban against the Northern Alliance in Afghanistan, according to U.S. intelligence.

The Musharraf government fingered Mehsud for Bhutto's death in December, but some members of her political party and her family have questioned those assertions. There have been complaints that the government failed to provide her adequate security and vague allegations that elements within the government might have been involved in the assassination.

In December, the Pakistani government released the transcript of a purported conversation in which an Al Qaeda operative reported to Mehsud that his men carried out the attack on Bhutto.

Rogers, who receives frequent intelligence briefings on Pakistan, told AP he has not seen definitive proof Mehsud's organization actually carried out the attack.

"We had good information that he was at least making the attempt to do it. If his folks were the first ones to do it I haven't seen that yet. I do believe he had every intention to kill Bhutto. I don't think you can say (he did it) that definitely."

Bhutto was a secular politician popular in the U.S. and other Western countries for her opposition to hard-line Islam. Mehsud has denied involvement in her death.