President George W Bush said on Saturday he was troubled by a US intelligence report that Al-Qaeda has become entrenched in a safe haven in Pakistan's tribal region near Afghanistan.
But Bush offered support for Pakistan's embattled president, saying he believes Pervez Musharraf is committed to fighting Al-Qaeda and Taliban militants.
Part of the National Intelligence Estimate made public this week found a "persistent and evolving" threat to the United States from Islamic militant groups, especially Osama bin Laden's Al-Qaeda.
Bush, in his taped weekly radio address, said the report's assessment that Al-Qaeda was gaining strengthen in the tribal region of Pakistan was "one of the most troubling".
The United States, after being hit by Al-Qaeda's attacks on September 11, 2001, led an invasion of Afghanistan later that year to oust the Taliban religious movement that had seized power and to root out bin Laden and his followers.
Musharraf, an army general, has been an important ally to Washington but must contend with a violent campaign by Islamic militants and porous mountain borders that make it hard to halt the flow of fighters, weapons, opium and other drugs.
The White House has acknowledged that a truce Musharraf reached in September with tribal leaders had not worked.
Bush, now more than four years into a war in Iraq that has stretched the US military, said Pakistan's tribal leaders had proven unwilling or unable to police the area themselves.
"President Musharraf recognizes the agreement has not been successful or well-enforced and is taking active steps to correct," Bush said.