An audio tape said to be by al-Qaeda deputy leader Ayman al-Zawahiri has been posted on a website - a week after an alleged US air strike targeting him.
Ayman al-Zawahiri was the alleged target of a US raid a week ago
The speaker praises Islamic fighters in Afghanistan but does not mention the strike - on a Pakistani village.
CIA experts in the US confirmed the voice was Zawahiri's but there is no evidence it is a recent recording.
The posting came a day after Arabic TV station al-Jazeera broadcast a message thought to be from Osama Bin Laden.
It is the first time Bin Laden has been heard from since December 2004.
A CIA spokesperson said in Washington of the latest posting: "Following technical analysis of the tape, the CIA has assessed that it is the voice of Ayman al-Zawahiri."
However, a US counter-terrorism official told the AFP news agency there was "no reason to believe it was done recently".
A number of foreign militants are said to have been killed in the raid
It could be "something that someone pulled off the shelf and decided to post", he said.
The 18-minute tape takes the form of a long poem praising the "martyrs" fighting Western forces in Afghanistan.
In his message, Bin Laden appeared to suggest that a US withdrawal from Muslim lands could bring about a truce. The US dismissed it as a "ploy".
Meanwhile, several thousand people joined an anti-US rally in the Pakistani city of Peshawar on Friday in protest at the missile strike, in which 18 people died.
The attack took place in Damadola village, in the Pakistani tribal area bordering Afghanistan.
Zawahiri is not thought to have been present at the time of the raid but Pakistan says a number of foreign militants were killed.
The US has about 20,000 troops in Afghanistan, but Islamabad does not allow them to operate across the border.
Pakistani Prime Minister Shaukat Aziz has said he intends to raise the issue with US President George W Bush when he meets him in Washington next week.
The US insists relations with Pakistan remain good and says it will continue to target militants.