The American Al Qaeda spokesman known as "Azzam the American" will be indicted Wednesday by a federal grand jury in Los Angeles, FOX News has confirmed.

Adam Yahiye Gadahn, whose exact whereabouts is unknown but is believed to be in Pakistan, is expected to be charged with material support and treason, sources told FOX News. It will be the first time an American has been charged with treason since 1952.

The treason charge, according to sources in Los Angeles and Washington, is based primarily on the statements Gadahn has made in his video presentations.

The Justice Department is expected to make the formal announcement later in the day.

A 48-minute video posted on an Islamic militant Web site last month included footage of Al Qaeda's No. 2 man, Ayman al-Zawahiri, and Gadahn, who the FBI believes attended Al Qaeda training camps in Pakistan and served as an Al Qaeda translator.

It was the second time the American-born Gadahn, 28, has appeared in the same video with al-Zawahiri. In a July 7 video marking the one-year anniversary of bombings against the London transit system, Gadahn appeared briefly, saying no Muslim should "shed tears" for Westerners killed by Al Qaeda attacks.

Officials, terror experts and members of the mosque Gadahn used to attend in California also believe that the man in a video aired in October 2004 also was Gadahn. The video shows a man wearing dark glasses and an Arab head gear wrapped around his face, claiming to be an American member of Al Qaeda and promising attacks that will make the streets of America "run red with blood."

Gadahn, the son of musician Adam Pearlman, was raised in a middle-class Jewish family, but at the age of 17 he dropped in on the Islamic Society of Orange County and asked to worship there. He later was expelled from the mosque after attacking an employee. Records show he pleaded guilty to assault and battery charges on June 11, 1997, and was sentenced to two days in Orange County jail and 40 hours of community service. It is believed he fled to Pakistan sometime in 1998.

Gadahn disappeared soon after the Sept. 11, 2001, attacks on New York and Washington.

As of May 27, 2004, court records showed that Gadahn failed to perform the community service, so a warrant is outstanding for his arrest.

Some of those who attended the mosque said Gadahn was becoming very extreme in his views, while family members said he began attacking Christianity as he became more a more devout follower of Islam.

According to the FBI, Gadahn attended Al Qaeda training camps in Afghanistan and served as an Al Qaeda translator. The agency said he also was associated with senior Al Qaeda lieutenant Abu Zubeida in Pakistan. He has used the aliases Adam Pearlman and Aby Suhayb Al-Amriki. The FBI also said Gadahn was known to have performed translations for Al Qaeda, among other services.

In 2004, FBI officials in Los Angeles said Gadahn was last known to be in Southern California in 1997 or 1998.

FOX News' Catherine Herridge and Ian McCaleb and The Associated Press contributed to this report.