The White House says the U.S. intelligence community believes the latest audiotape purportedly from al-Qaida leader Osama bin Laden is authentic.
The tape aired on Sunday on the Arabic broadcasting network Al-Jazeera.
A White House spokesman, Scott McClellan told reporters the tape shows the al-Qaida leadership is on the run and is under a lot of pressure.
On the tape, a man identified as bin Laden accuses the West of waging what he called a "crusader-Zionist war" against Muslims.
The speaker says evidence of that is the conflict in Sudan's Darfur region and the West's decision to cut off funds to the Hamas-led Palestinian government. Analysts say the Hamas reference indicates the tape was made recently.
The speaker also calls on al-Qaida members and supporters to go to Sudan to be ready to fight proposed U.N. peacekeepers, whom he called crusader plunderers.
The tape also says Westerners are complicit in the actions of their governments, a statement analysts say is meant to justify terrorist attacks on civilians.
A Hamas spokesman distanced the group from the voice on the tape. He said Hamas has taken positions different from the ones expressed by Osama bin Laden.
The tape is the first from bin Laden since a January recording in which he threatened more attacks against the United States. He also offered a truce on that tape, which the White House rejected.