Holding Al Qaeda and Taliban commander Baitullah Mehsud responsible for the assassination of former Pakistan prime minister Benazir Bhutto [Images], the Central Intelligence Agency of the United States said the nexus between local and international terrorists was a grave threat to the stability of Pakistan.

The agency concluded that these elements were also behind the recent wave of suicide bombings and attacks in the country.

The CIA's findings were in consonance with Pakistan government's claim about the dastardly killing of the Pakistan People's Party leader.

"This was done by that network around Baitullah Mehsud. We have no reason to question that," CIA director Michael V Hayden said in an interview to the Washington Post.

"What you see is a change in the character of what's going on there. You've got this nexus now that probably was always there in latency, but is now active; a nexus between Al Qaeda [Images] and various extremist and separatist groups. It is clear that their intention is to continue to try to do harm to the Pakistani state as it currently exists," he added.

'Al Qaeda is right under Musharraf's nose'

However, Hayden declined to discuss the intelligence behind CIA's assessment.

The relationship between Al Qaeda and local insurgents has always been a matter of concern for the US and it helped members of the terrorist outfit to regroup and rebuild in the restive Pakistan-Afghanistan border region, Hayden explained.

''We've always viewed that to be an ultimate danger to the United States, but now it appears that it is a serious base of danger to the current well-being of Pakistan," Hayden said.

The top US intelligence official said the agency was engaged in the region ever since the 9/11 attacks and it remained one their 'highest priorities'.

He described Pakistan's role in the war on terror, saying "The United States has not had a better partner in the war on terrorism than the Pakistanis. The turmoil of the past few weeks has only deepened that cooperation," he said, adding the two countries now had 'even more clearly mutual and common interests'.

Hayden admitted that combating extremism in a country 'divided by ethnic, religious and cultural allegiances' was far more difficult that it seems.