A man who set himself on fire in front of the White House this week was a key witness against a sheik accused of funneling millions of dollars to Al Qaeda (search) and the Palestinian Islamic group Hamas, defense lawyers said Tuesday.

Defense attorneys said Mohamed Alanssi is a confidential informant central to the prosecution of Sheik Ali Hassan al-Moayad, a leading member of an Islamic-oriented political party in Yemen who is awaiting trial in federal court in New York. He and his assistant allegedly conspired to provide material support to Usama bin Laden (search) and the Hamas (search).

Alanssi sent suicide notes Monday morning to his FBI handler and a Washington Post reporter, complaining about his treatment by the government and threatening that he would burn himself in an "unexpected place."

He arrived at the White House gate later that day with a letter addressed to President Bush, pulled a lighter from his pocket and set his clothing ablaze. He was hospitalized in serious condition Tuesday.

Federal prosecutors and the FBI declined to comment on the case. But attorneys for al-Moayad and his co-defendant, Mohammed Mohsen Yahya Zayed, said Tuesday they believe the government case was seriously weakened by the incident and Alanssi's suicide notes. The newspaper published Alanssi's letters on its Web site.

Alanssi, a 52-year-old Virginia resident, wrote to FBI agent Robert Fuller in New York complaining that the agent had ignored Alanssi's request to visit his ailing wife and family in Yemen. He threatened not to testify against al-Moayad as a result. He wrote the Post that he was afraid the government might jail and torture him if he stopped cooperating.

In what the Post described as a series of recent interviews, Alanssi also said that some FBI agents told him he would "be a millionaire" and receive permanent U.S. residency in exchange for his cooperation, the newspaper reported.

Defense lawyers in the al-Moayad case said Alanssi's allegations reveal the tremendous pressure he was under to produce evidence against al-Moayad and Zayed, the sheik's Yemeni assistant.

"This was a manufactured crime and Alanssi had a very strong motive to ensnare these people," said Zayed's attorney, Jonathan Marks.

Alanssi served as a translator between an FBI informant posing as a convert to Islam and al-Moayad and Zayed. The undercover FBI informant had said he wanted to send money to Al Qaeda and Hamas, according to transcripts of their recorded conversations.

"He is the man who is the contact between the government and my client," said al-Moayad's attorney, Howard Jacobs. "His credibility is at great issue in the case."

In documents filed hours after Alanssi set himself on fire, Marks wrote that Alanssi's translations were "inaccurate, incomplete and frequently embellished."

The trial is scheduled to begin in January.