Bin Laden was shown in mountainous terrain
The CIA says an audiotape of al-Qaeda leader Osama Bin Laden broadcast on Arabic television this week was "probably" genuine.
"The voice is probably that of Osama Bin Laden," an unnamed CIA official said.
The official said analysts had been unable to determine when the video footage featuring Bin Laden and his aide Ayman al-Zawahri and separate audio recordings were made.
"Keep in mind that there are no date specific references in his portion of the tape, and therefore it could have been recorded at any time," he said.
On Thursday, the CIA said it was confident that an audio recording of al-Zawahri was authentic.
Two audio recordings were played on al-Jazeera TV along with previously unseen video footage of the two men.
The Qatar-based channel said the recording had probably been made in April or early May in an "undetermined mountain area".
The videotape was aired on the eve of the second anniversary of the 11 September attacks on New York and Washington, which have been blamed on Bin Laden's al-Qaeda network.
And on Friday, al-Jazeera broadcast what it said was a new videotape showing one of the suspected 11 September hijackers.
"America is the enemy that every Muslim should fight. There is no way the Arab nation can be saved except through jihad [holy war]," said the speaker, identified as Saeed al-Ghamdi.
On one of the audiotapes, a man purported to be Bin Laden praises the 11 September attackers. In the other a voice thought to be Mr Zawahri calls for Iraqi guerrillas to "bury" US troops.
The BBC's security correspondent Frank Gardner says the latest video is important because it is the first new footage of Bin Laden seen in more than a year, even though there is no independent confirmation that it was actually filmed this year.
It was almost certainly shot in Afghanistan or Pakistan, he says.
The voice said to be Bin Laden's called for emulation of the hijackers who crashed airliners into the World Trade Center and Pentagon on 11 September 2001.
"Whoever wants to learn loyalty and courage in support of religion should learn from [Said] al-Ghamdi, Mohammed Atta, Khaled al-Mihdhar, Ziad Jarrah, Marwan al-Shehhi and the others," the speaker said.
The other speaker urged Iraqis to "rely on God and devour the Americans, like lions devour their prey - bury them in the Iraqi graveyard".
The speaker also called on Palestinians to resist Israel.
"We call on them to stand fast on the path of jihad [holy war] and not to be deceived by the tricks of America and its agents who bless the roadmap to hell. Palestine will only be liberated with jihad."
Referring to the 11 September attacks and the US campaigns in Afghanistan and Iraq, he warned that "what you have seen so far is only the first skirmishes and the beginning of the clash".
"The real battle, however, has not started yet. So prepare yourselves to be punished for your crimes."