An Islamist website broadcast an audio tape purported to be the voice of Osama bin Laden telling Muslims to fight against the "enemy" United States, and said it had been made to mark last week's Muslim feast of Eid al-Adha.
If authenticated, the recording would be the most recent proof that bin Laden had escaped the 2001 US-led military campaign to flush him and his al-Qaeda operatives from Afghanistan.
"Regarding this Zionist Crusader war on the nation of Islam, it is the duty of Muslims to fight for the sake of God and to incite the faithful to fight the infidels," the recording said.
"It is the utmost duty to fight the enemy that sabotages the world. Jihad is a necessity for Muslims today, you must all fight to uphold the truth," it added.
"The only way to deal a decisive blow in the conflict with the enemy is through killing and fighting."
The website did not give a specific date for when the recording was made or when it was posted.
The Saudi-owned Al Hayat newspaper first published excerpts of the recording on Sunday, which it said could be found on the Islamist "Jihad Forum" site, hosted by the www.arabforum.net website.
It follows another audio tape broadcast last week by Qatar's al-Jazeera television network in which the Saudi-born militant called on Muslims to use suicide attacks and bombings to prevent a US war on Iraq. Jihad Forum said the new message was made on the occasion of the three-day Eid feast.
Bin Laden started the message by identifying the United States and its "foolish" President George W. Bush as the enemy of all Muslims and said it was waging a "Zionist Crusader" campaign to carve up the whole region.
"The United States' goal to divide the Middle East is not just a passing fancy," the al Qaeda leader said. "The only way to defeat the infidels is holy war and to incite Muslims."
Bin Laden also urged Muslims to set aside their fear of the United States and fight it.
"Oh Muslims, do not fear America because we have defeated them repeatedly and they are the most cowardly of people when you meet them face to face," he declared.
In the recording, bin Laden lauded the wars Muslims had fought and won against Western Crusaders throughout history and recounted the times that Muslim militants - some from his own al-Qaeda network - had bombed US and Western targets in Saudi Arabia, Yemen, Somalia and Kenya and Tanzania.
The recordings coincide with a state of high alert in the United States and its ally Britain who said they had concrete information that al-Qaeda was planning a slew of attacks.