Al-Qaeda may have started losing the support of the Islamic world due to its use of violence, especially against Muslims, a top United States intelligence official has said.

"Are we reaching a tipping point to witness the decline of this radical behaviour? We don't know the answer to that yet, but we're watching it very closely," National Intelligence Director Admiral Mike McConnell told the House Select Committee on Intelligence.

"Brutal attacks unleashed by the al-Qaeda and its affiliates against Muslim civilians have tarnished al-Qaeda's self-styled image as the extremist vanguard," he said.

McConnell and Central Intelligence Agency Director General Michael Hayden cited falling donations and criticism of al-Qaeda by other fundamentalists as indicative of the shift of opinion against the group.

"In the last year to 18 months, al-Qaeda has had difficulty in raising funds and sustaining themselves," McConnell said, while Hayden said that there seems to be increasing willingness in the Islamic world to question al-Qaeda's vision.

McConnell also said that hundreds of al-Qaeda's leadership, operational, media, financial, logistics, weapons, and even their foreign fighter facilitators have been 'neutralised' in recent years, but added that the terrorist group remains a prominent threat to the US.

"Despite our successes over the years, the group has been able to regenerate many of its key capabilities, and that includes the top leadership, operational lieutenants, and, most importantly, a de facto safe haven in Pakistan's border area with Afghanistan," he said.

While acknowledging that the al-Qaeda enjoyed a safe haven in Pakistan's tribal areas, McConnell praised the Musharraf government for its cooperation in the war on terror.

"The Pakistani authorities, who are our partners in this fight and have helped us more than any other nation in counter-terrorism operations, are determined to strengthen their performance," he said.

The intelligence chief favoured more aggressive activity by US forces in Pakistan, but added, "what that connotes is a potential to invade a sovereign country. So that becomes a very problematic issue".