An FBI informant who set himself on fire in front of the White House will be called as a witness for the defense of a Yemeni sheik accused of aiding Hamas (search) and Al Qaeda (search), defense attorneys said Friday.

Lawyers for Sheik Mohammed Ali Hasan al-Moayad (search) and his assistant said they have subpoenaed Mohamed Alanssi (search), who helped build the FBI's case by posing as the go-between for al-Moayad and another informant playing an American Muslim who wanted help funneling millions of dollars to terrorists.

"It is our intention to call Mohamed Alanssi in our case," Howard Jacobs, a lawyer for al-Moayad, said before the start of testimony Friday morning in federal court in Brooklyn.

Lawyers for al-Moayad and his assistant, Mohammed Mohsen Yahya Zayed, said they expected Alanssi to testify next week.

The decision is a high-stakes gamble for defense lawyers, who want to undermine the prosecution by introducing questions about Alanssi's credibility and troubled personal history. Alanssi is the sole source of some of the government's most dramatic claims about al-Moayad, including the allegation that the sheik said he personally handed $20 million to Usama bin Laden.

Defense lawyers said they would request the unsealing of a bank fraud case filed against Alanssi last year.

Alanssi was to have been the star prosecution witness until he set his clothing on fire in front of the White House last November to protest what he called the FBI's failure to make good on promises of wealth and American citizenship.

The government dropped him from its witness list and instead relied on hours of secretly recorded meetings with Alanssi; al-Moayad, Zayed and the self-described radical U.S. Muslim, who in fact was a second FBI informant.

Without Alanssi, the case began to center almost entirely on the Hamas allegations. Then-Attorney General John Ashcroft had portrayed the case as a major blow against Al Qaeda when the charges were unsealed in 2003.

On the surveillance tapes, Al-Moayad and Zayed appear to promise to help the informants donate $2.5 million to Hamas, with a 10 percent commission for the defendants' Yemeni charities. Defense lawyers said al-Moayad and Zayed never intended to pass the money to the Palestinian militant group and simply said what they believed the informants wanted to hear.

But jurors last week saw al-Moayad and Zayed on the tapes discussing code words for ammunition and weapons and condemning Americans and Jews in meetings with the informants and alone in their German hotel room. Defense lawyers acknowledged that the evidence was potentially damning.

Al-Moayad is accused of material support for terrorism, as well as conspiring and attempting to provide material support. He could receive a 60-year prison sentence. Zayed faces the conspiracy and attempt charges. He could serve three decades behind bars.