Officials believe in tape's validity, differ on clues about bin Laden.

Byline: Stephen J. Hedges

WASHINGTON _ U.S. government officials said Wednesday that they are treating an audiotape purported to be from Osama bin Laden as authentic, but they and terrorism experts differed on whether the four-minute message suggests that the al-Qaida terrorist network bin Laden leads is regaining its strength or has been hobbled by the U.S. war on terrorism.

Aired by the Arab television network Al-Jazeera, the tape warns the U.S. and its allies, "It is time we get even. You will be killed just as you kill, and will be bombed just as you bomb," according to a U.S. government translation.

If genuine, the message would be the first from bin Laden since November, when he appeared on videotape.

"It's a very strident message," one U.S. official said. "There are probably a number of purposes to it: to boost moral in the rank and file, to let them know the senior leadership's still around and, around the world, to try and…