WASHINGTON -- The International Committee of the Red Cross will soon visit an American citizen who was picked up on Syria's battlefield two weeks ago and is being held by U.S. forces in Iraq, U.S. officials said Thursday. The Pentagon has accused the man of fighting for the Islamic State group.

The unidentified American surrendered to U.S.-backed Syrian Democratic Forces around Sept. 12, and has been detained since then as an unlawful enemy combatant.

He is being held at a detention facility in Iraq, according to senior U.S. officials, who weren't authorized to discuss the detainee's location publicly and spoke on condition of anonymity.

Ben Sakrisson, a Pentagon spokesman, said the Red Cross was notified of the man's detention this week. The humanitarian agency confirmed that account.

"We are following up with the U.S. authorities to organize a visit," said Marc Kilstein, ICRC spokesman in Washington. He said the group expects "timely access" and the ability to speak with him in private.

U.S. officials haven't said what they'll do with the man.

The senior officials said it was not clear yet if he would be turned over to the U.S. Justice Department. Another possibility could involve handing him over to Iraqi authorities if he is believed to have committed war crimes in Iraq while working with IS in the region.

The man's fate has raised questions among constitutional lawyers and human rights monitors in the United States.

"The U.S. government cannot continue to operate in the shadows on this case," said Daphne Eviatar of Amnesty International. "It should be treating this detainee humanely, providing him a meaningful opportunity to challenge his detention, in a legitimate facility that is not at Guantanamo. And any prosecution should be fair and open, in a legitimate court."

The senior officials have suggested it is unlikely he would be sent to the U.S. detention centre at Guantanamo Bay, Cuba. But no one has publicly ruled out that option. And President Donald Trump has championed the facility that his predecessors sought to close, saying he wants to fill it up with "bad dudes."

In recent years, suspects accused of terror-related offences, including Americans, routinely have been adjudicated in U.S. courts.

A Virginia man who fought with IS in Syria and Iraq for several months surrendered to Iraqi Kurdish forces in northern Iraq in March 2016 and was flown back to the U.S. to face charges. A jury in a federal court in Virginia took only four hours to convict Mohamad Khweis, 27, of Alexandria, Virginia, on terrorism charges.

Associated Press writer Deb Riechmann contributed to this report.