WASHINGTON -- Osama bin Laden's top field commander is talking.
Trouble is, his American interrogators don't know whether to believe him.
Abu Zubaydah already has given information that led to last week's alert to financial institutions in the northeastern United States, U.S. officials say. He has also claimed that al-Qaida knows how to build a "dirty bomb" designed to spread radioactivity over a wide area.
Neither piece of information surprised American authorities. U.S. intelligence already had obtained similar nonspecific threats to banks, and bin Laden's quest for weapons of mass destruction is well-known.
But because the information came from Abu Zubaydah, the interrogators took note. Officials describe the Saudi-born Palestinian as the connection between bin Laden and many of al-Qaida's operational cells.
"He's talking, but the issue is sorting out what's true and what's not, what is reality and what is mere boasting," said one U.S. official familiar with the interrogation. "That's going to take some time."
A better source may be his notebook, found when he was captured in a joint Pakistani-U.S. raid March 28 in Faisalabad, Pakistan. A defense official said it contains information that could indicate more terrorist attacks are in the works, but its import isn't fully clear.
Context is crucial, the official said. "Are these his ideas, his plans, his musings?"