The Justice Department is preparing to charge Ali Saleh Kahlah al Marri, the only "enemy combatant" currently held on U.S. soil, for his alleged role in terrorist activities, according to a source with knowledge of the case.

The source says that a formal filing of charges is "imminent," and those charges are expected to be filed in Illinois, where he was first arrested a few months after the Sept. 11 attacks.

At the time, al-Marri was charged with credit card fraud and other crimes. But in June 2003, President Bush declared al-Marri an "enemy combatant," accusing him of being a sleeper agent.

Authorities transferred him to a Navy Brig in South Carolina, where he has been ever since.

Charging al-Marri would indicate a major shift from the Bush Administration, which insisted that al-Marri should face a military tribunal and stay out of the civilian court system.

The source says that the Justice Department has informed Al-Marri's legal team that charges are likely. Another source tells FOX News that at least one of al-Marri's lawyers, Jonathan Hafetz of the American Civil Liberties Union, is currently in South Carolina.

A woman who answered the phone at the ACLU could not say if he is there for a matter related to the al-Marri case, and he did not return a phone call.

Al-Marri and his legal team have challenged his detention, insisting that he has been subjected to torture and other cruel, inhuman, and degrading treatment. They say he is currently in solitary confinement "under severe restrictions" and has not seen his family in nearly six years, speaking to them only a couple of times.

The Supreme Court is currently expected to hear his challenge sometime in April. New York University's Brennan Center, which is representing al-Marri, says on its web site that they have "long argued that Americas criminal justice system can and should handle cases in which individuals are accused of terrorism." It looks like they are going to get their wish.

Asked about the latest developments at a briefing today, White House Press Secretary Robert Gibbs declined to comment.

FOX News' Catherine Herridge contributed to this report.