But despite its own intelligence community's misgivings, the US administration of George W. Bush is standing by President Pervez Musharraf as Pakistan's military ruler faces one of his gravest crises yet.

"Musharraf is a strong ally in the war against these extremists. I like him and I appreciate him," President Bush said Tuesday after Pakistani forces stormed a pro-Taliban mosque sheltering scores of women and children.

In an audiotape posted on the Internet, al-Qaeda second-in-command Ayman al-Zawahiri urged Pakistanis to revolt against Musharraf following the assault on the Red Mosque in Islamabad, which left at least 82 people dead.

The threat coincided with a new US intelligence report suggesting al-Qaeda is gaining strength and has established a safe haven in remote tribal areas of western Pakistan for training and plotting attacks, The Washington Post reported Thursday.

The intelligence assessment, which is due to be discussed at a White House meeting on Thursday, concludes the group has rebuilt itself despite extensive US efforts to destroy the network, the paper wrote.

Appearing before Congress Wednesday, top US intelligence officials fretted that more aggressive action against extremists sheltering inside Pakistan's anarchic northwest could spark a broader anti-Musharraf uprising.

"It is not too great an exaggeration to say there is some risk of turning the problem in northwest Pakistan into the problem of all of Pakistan," argued Thomas Fingar, deputy director of national intelligence.

The United States remains fearful of undermining a key "war on terror" ally even as criticism mounts that it is getting little in return for huge sums lavished on the Musharraf regime since the September 11 attacks of 2001.

A secret US operation in early 2005 to capture senior al-Qaeda members in Pakistan's tribal areas was aborted at the last minute after top officials decided it was too risky and could jeopardize relations with Islamabad, the New York Times reported this week.

Fingar was pressed on why bin Laden was still at large and Afghanistan's Taliban were resurgent despite estimated funding of 10 billion dollars extended by Washington for Pakistani counter-terrorism operations.

"The answer has to be yes, that provision of assistance should be properly tied to expected outcomes," he told a hearing of the House of Representatives armed services committee on global security threats.

"And the outcomes for which people have committed, they should be held accountable for."

John Kringen, the CIA's director of intelligence, said al-Qaeda and Taliban extremists appear "fairly well settled into the safe haven" of northwest Pakistan, benefiting from more training, money and communications.

Kringen expressed particular regret over Musharraf's peace deal last September with tribal elders in North Waziristan.

The Waziristan region is a hotbed of pro-Taliban militants supporting the bloody insurgency in Afghanistan against the US-backed government of President Hamid Karzai.

"We would agree that the peace deal in Waziristan has not been helpful in terms of the anti-terrorist effort," the Central Intelligence Agency official said.

Musharraf's rationale for the controversial peace pact was to halt cross-border attacks and enlist tribal help to expel al-Qaeda fighters.

"From our assessment, we have not seen developments going in that direction but actually in a negative direction," Kringen said.

Fingar said that Musharraf looks weaker after massive pro-democracy protests sparked by his suspension in March of Pakistan's chief justice.

"With tribal opposition to the US military presence in Afghanistan and Iraq widespread and elections expected later this year, the situation will become even more challenging -- for President Musharraf and for the US," he warned.