A key al-Qaida leader has called for revenge against Israel's offensives in Lebanon and the Gaza Strip. President Bush says he is not surprised.

Undated video broadcast of Ayman al-Zawahiri

Al-Qaida's second-in-command says the terrorist group will not remain silent while Israeli attacks "burn our brothers."

In a taped message broadcast by the al-Jazerra television network, Ayman al-Zawahiri called for Muslims to rise up and become martyrs in a global Jihad against Israel and what he called the crusader coalition.

He said war with Israel does not depend on cease-fires. It is a jihad that will last, he says, until religion prevails from Spain to Iraq. "The entire world is an open battlefield for us," Zawahiri said.

It is his 10th taped message of the year, but the first from al-Qaida since fighting between Israel and Hezbollah militants in Lebanon began more than two weeks ago.

Asked about the tape during an Oval Office meeting with the President of Romania, President Bush said he is not surprised that other terrorists are starting to speak out in support of Hezbollah.

George W. Bush

"Zawahiri's attitude about life is that there should not be free societies," said Mr. Bush. "And he believes that people ought to use terrorist tactics - the killing of innocent people - to achieve his objective. And so I am not surprised that he feels like he needs to lend his voice to terrorist activities that are trying to prevent democracies from moving forward."

With al-Qaida's strength significantly reduced, White House spokesman Tony Snow believes the new threats are part of Zawahiri's efforts to remain relevant, or to "stay in the game."

Observers say it may also signal the willingness of the largely Sunni organization to set aside sectarian differences and help the predominantly Shi'ite Hezbollah movement in its fight against Israel.