A picture taken on December 29 from a village in southern Idlib, shows smoke billowing following reported airstrikes on the village of Um Jalal in Syria's northwestern Idlib province. (Omar Haj Kadour/AFP/Getty Images)

An unidentified American allowed to speak with the ACLU by a federal court has asked the group to challenge his nearly four-month detention without charges by the U.S. military in Iraq.

He was moved to Iraq after being captured in Syria when he surrendered on a battlefield and was held as an enemy combatant and a suspected member of the Islamic State, the government has said.

In a court filing, ACLU attorneys said the U.S. citizen informed them of his wishes during a video conference arranged through the Pentagon on Wednesday morning. The video conference was set up after U.S. District Judge Tanya S. Chutkan of the District of Columbia on Dec. 23 ordered the Defense Department to give the civil liberties group access to the man.

The ACLU did not disclose details of the call, which was arranged but not monitored by U.S. authorities, but told the court the man indicated he wanted to assert his constitutional right to challenge the basis for his detention and for the ACLU to represent him in court.

The ACLU asked Chutkan to require a prompt response by the government and to continue to bar the government from transferring the detainee to a third country.

Chutkan directed the government to respond by 5 p.m. Monday.

"The Trump administration illegally denied an American his rights to access a lawyer and a court for nearly four months, but those efforts have finally failed," ACLU attorney Jonathan Hafetz said in a statement. "Now that our client has secured the judicial review that the government attempted to block, he looks forward to establishing the illegality of his detention."

"We are reviewing the filing," Justice Department spokesman Wyn Hornbuckle said, noting that the court gave the government until Monday to file its response.

The U.S. government has sought to throw out the ACLU's case, arguing that the government can secretly hold the man without court review for a to-be-determined "reasonable period" and that the ACLU did not know the unnamed American or his family so it could not establish legal standing to sue on his behalf.

As a result, the Justice Department argued, the court had no authority to weigh in on wartime detentions by the U.S. military in an overseas conflict zone. The man held has not been identified in court filings.

Chutkan rejected what she called the government's request for a "blank check" in such cases, calling its argument "disingenuous at best" and "troubling," since it was the Defense Department that was withholding his identity, preventing his access to a lawyer and hindering efforts to find his relatives.

Chutkan noted that the government had acknowledged that the man asked for a lawyer after being read his Miranda rights when his questioning shifted from probing for intelligence-gathering to an interrogation for law enforcement purposes.

"Having informed the detainee of his right to counsel, and the detainee having asked for counsel, the department's position that his request should simply be ignored until it decides what to do with the detainee and when to allow him access to counsel is both remarkable and troubling," Chutkan had written in the case.

The American's case could test for the first time whether the right — established by the U.S. Supreme Court during George W. Bush's presidency — of U.S. citizens suspected of belonging to al-Qaeda and other terrorist groups after the Sept. 11, 2001, attacks to challenge detentions after their capture on a battlefield also applies to suspected Islamic State fighters.

The government has said the man surrendered in Syria to rebel Syrian Democratic Forces and was turned over to the U.S. military on Sept. 14 and has been held since in military custody in Iraq.

The government has said it is complying with the Geneva Conventions in not releasing his name and that he has been visited by the International Committee of the Red Cross.

The case has been vexing for U.S. authorities. The Washington Post reported in October that Justice Department officials did not think they had enough evidence to charge the man, who invoked his rights to an attorney, halting his interrogation.

Officials told The Washington Post that the man once had ties to the Pacific Northwest but that most of his family and roots are in the Middle East. The New York Times reported that the Trump administration was considering transferring him to Saudi Arabia under restrictions and that the man was a dual Saudi national.

The man could be turned over to Iraqi authorities for trial. But conviction would require evidence, and it is against U.S. law to send prisoners to a country where they could face torture, which Human Rights Watch says is rampant in Iraq. He also could be sent to the U.S. detention facility at Guantanamo Bay, Cuba, which would invite immediate litigation.