The US intelligence chief has named Pakistan as the centre of an Al Qaeda network where its top leaders were holed up, a charge rejected on Friday by Islamabad, which said it had done more than any other nation to fight terrorism.

Director of National Intelligence John Negroponte told the Senate Select Committee on Intelligence in testimony on Thursday that Al Qaeda leaders had found a haven in secure hideouts in Pakistan.

He said Pakistan was at the centre of an Al Qaeda ring that stretched to Middle East, Africa and Europe. Lt Gen Michael Maples, chief of the Pentagon's Defense Intelligence Agency, testified that while Islamabad's help had led to the arrest or killing of many terrorists, Pakistan's border with Afghanistan 'remains a haven for Al Qaeda's leadership and other extremists.'

Maples also said tribal leaders in North Waziristan, which borders Afghanistan, had 'not abided by most terms' of an agreement signed in September last year with the Pakistan government. Under the pact, the tribes agreed to stop attacks on Pakistani forces and expel foreign militants.

"Al Qaeda's network may exploit the agreement for increased freedom of movement and operations," Maples said.

Negroponte said Al Qaeda leaders holed up in Pakistan were rebuilding a network that was decimated by the capture and killing of hundreds of the group's cadres since the 9/11 terror attacks in the US.

He said Pakistan was a 'major source of Islamic extremism.'

Negroponte also warned of a potential war between India and Pakistan despite improved relations between them. He said, however, the neighbours 'do not appear to be engaged in a Cold War-style arms race based on a quest for numerical superiority.'

Pakistan, however, said that the US had not given it any information about Al Qaeda leaders sheltering in its territory and Negroponte should have taken into account the fact that successes against terrorists were made possible by its help.

Pointing out that the focus should be 'on cooperation instead of questionable criticism,' Pakistan's foreign ministry spokesperson Tasnim Aslam said, "In breaking the back of Al Qaeda, Pakistan has done more than any other country in the world."

"There is no existence of Al-Qaeda in Pakistan and the group has been marginalized," Pakistan's Interior Minister Aftab Khan Sherpao told media persons in Islamabad after a meeting with the US Assistant Secretary of State Richard Boucher.

Boucher is in Islamabad to hold talks with President Pervez Musharraf on a host of issues, including tensions over allegations that Pakistan has not cracked down hard on Taliban.

"Al-Qaeda is not operating from Pakistan," Sherpao said, adding that Islamabad had made it clear several times previously too.