A radical New York imam who was once investigated as a possible co-conspirator in the 1993 bombing of the World Trade Center will share the stage Saturday night as a featured guest and speaker when the Council on American-Islamic Relations celebrates its 15th anniversary in Washington.

Siraj Wahhaj, imam of the Masjid Al-Taqwa mosque in Brooklyn, N.Y., became the first Muslim to lead the opening prayer in the U.S. House of Representatives in 1991. Four years later, he was a character witness for Omar Abdel-Rahman, the so-called "blind sheik" convicted of conspiring to bomb the World Trade Center in 1993. Although Wahhaj was never charged, then-U.S. Attorney Mary Jo White identified him in 1995 in a list of "unindicted persons who may be alleged as co-conspirators."

Also speaking at the event will be the Rev. Jesse Jackson.

Stephen Schwartz, executive director of the Center for Islamic Pluralism, a Washington-based think tank, calls Wahhaj one of the most prominent and strident African-American Islamic preachers in America.

"He's a hatemonger, there's no question about it," Schwartz said. "He's the No. 1 advocate of radical Islamic ideology among African-Americans. His stuff is very appealing to young Muslims who are on a radical path."

Schwartz identified Wahhaj — born in New York as Jeffrey Kearse — as a "leading radical Islamist" in "Black America, Prisons and Radical Islam," a 2008 report by his organization. According to the report, which cited Federal Bureau of Prisons figures, some 175 titles of Wahhaj's literature were found in prison libraries that year.

Schwartz said Wahhaj's writings seek to radicalize Muslims behind bars, particularly African-Americans. Saturday's speech, he said, will likely appeal to Muslims who feel they've been targeted recently by conservatives.

"He'll get up and say American Muslims are under attack, that their civil rights are being denied," Schwartz said. "He'll say that anybody who questions the community of these Muslim groups, that they're agents of the Zionists. He'll say that the criticism of CAIR, and of him, is all racism, the evil work of the Zionists and the media, and he'll say that American should get out of Afghanistan and any involvement in the Muslim world."

CAIR's banquet, "Leading the Change: 15 Years of Service," will be held Saturday night at the Marriott Crystal Gateway in Arlington, Va., just across the Potomac River from the Pentagon, where 125 people died during the Sept. 11, 2001, terrorist attacks.

Ibrahim Hooper, a spokesman for the Muslim civil liberties and advocacy organization, said foreign affairs and "lessons learned" from the civil rights movement are potential issues to be covered at the event, which will be closed to the press — although members of the press are welcome to buy a $65 ticket and attend as guests.

"You can buy a ticket," Hooper said. "Fox is free to come and harass us if you want."

Asked what Wahhaj and Jackson plan to say in their speeches, Ibraham characterized the inquiries as attempts to make "an ordinary dinner" a reason "to tarnish us or harass us."

"At some point," Hooper said, "it becomes a level of harassment when we're trying to exercise our civil rights as Americans."

Multiple calls seeking comment from Jackson and Wahhaj, who was said to be traveling this week in advance of the banquet, were not returned.

Wahhaj, a former member of the Nation of Islam who reportedly once called the FBI and CIA the "real terrorists," denied any involvement in the 1993 World Trade Center bombing.

"Law enforcement has never come to me and asked me any questions about any of these allegations," Wahhaj told Foxnews.com last year. "I have never participated in any planning against this nation."

Steven Emerson, executive director of The Investigative Project on Terrorism, said Wahhaj told a group of Muslims in New Jersey in 1992 that they could take over the country and institute a caliphate if they united.

"Brothers and sisters, if we unite, nobody can stop us," Wahhaj said, according to material provided by Emerson. "You wouldn't have to vote for Bush or Clinton ... If we were united and strong, we'd elect our own emir and give allegiance to him. ...

"Take my word, [if] 6 to 8 million Muslims unite in America, the country will come to us. Strong Muslims, strong and free, firm believers in Allah, I'm telling you, the rest of the world will come to the Muslims."

Emerson said Wahhaj, whom he described as a "full-fledged" radical, will tone down his rhetoric on such a stage.

"He'll obviously be careful," Emerson said. "They know he's being watched. He'll talk about how CAIR is under attack, Muslims are under attack, his typical spiel."

Louay Safi, director of communications and leadership development at the Islamic Society of North America, defended Wahhaj, a former member of the group's board of directors, as a "sought-after speaker" among Muslim circles.

"He's a very popular motivational speaker," Safi told Foxnews.com. "The sad thing is that the public is only allowed to see him through the veil of an unindicted co-conspirator. He has been charged in the press."

Safi urged Wahhaj's critics to consider context while reviewing his controversial statements in the past.

"Remember, he is a motivational speaker," he continued. "If you take statements by anyone, from the president to congressmen to anyone else, you can take one sentence out of context."

Safi also credited Wahhaj's work in revitalizing the Bedford-Stuyvesant section of Brooklyn, where in 2003, Brooklyn Borough President Marty Markowitz declared Aug. 15 "Imam Siraj Wahhaj Day" in honor of a lifetime of "outstanding and meaningful" achievement.

"He's done a lot of good work in his community, clearing the area of drug addicts and trying to foster a great sense of community," Safi said. "He's done a lot of good work in the New York area."