The conclusion of the CIA was revealed by Hayden in an interview with the Washington Post published yesterday.

The named men were also behind a new wave of violence threatening Pakistan's stability, he said.

Hayden said Bhutto was killed by fighters allied with Mehsud, a tribal leader in northwestern Pakistan, with support from al-Qaida's terrorist network.

That view mirrors the Pakistani government's conclusion.

The same alliance between local and international terrorists poses a grave risk to the government of Pakistani President Pervez Musharraf, a close US ally in the fight against terrorism, Hayden said.

However, some Bush administration officials outside the CIA who deal with Pakistani issues were less conclusive, with one calling the assertion "a very good assumption."

One of the officials said there was no "incontrovertible" evidence to prove or rebut the assessment.