An Islamic State flag in Raqqa in 2014. (Stringer/Reuters)

U.S. military officials plan to release an American citizen accused of supporting the Islamic State “under safe conditions,” and with $4,210 and a new cellphone near the Syrian town where he was first captured in September, according to a new filing Thursday in the unusual case.

The intended release would be done over the objections of the man, who has been held without charges in U.S. military custody in Iraq.

The American Civil Liberties Union, which has been representing the man, asked a federal judge in Washington Thursday night to block the action, which it had condemned as “disgraceful” and a de facto “death warrant.”

U.S. District Judge Tanya S. Chutkan scheduled a hearing on the government plan for Friday morning.

The cash is the same amount the man was carrying when he was taken into custody, the government said.

The details of the government’s plans for the man, identified in filings as John Doe, came in an affidavit from a Defense Department official, who described the release as “traditional military practice that is employed in the U.S. Central Command area of responsibility” and consistent with the military’s “obligations under the law of war.”

“The release plan sounds crazy at first blush, but you have to keep in mind that Doe voluntarily went to Syria to begin with,” said Bobby Chesney, an expert in national security law at the University of Texas School of Law.

It’s common in war detention settings, he said, to return someone to “the point of capture — at least if it’s safe to do so, and that’s one of the questions for the court.”

The expected legal battle over the man’s release is the latest twist in the case that has tested whether U.S. citizens captured on a battlefield as suspected “enemy combatants” have the right to challenge their detentions.

Nine months ago, the man was turned over to U.S. forces after he was captured at a rebel Syrian Democratic Forces checkpoint in Syria and declared his American citizenship. He grew up in Saudi Arabia and also has Saudi citizenship.

The man was questioned for U.S. intelligence purposes, but American officials said they lacked admissible evidence to charge him with a crime.

Instead, the government announced plans in April to transfer the man, against his will, to a third country that was not publicly identified.

Last month, the U.S. Court of Appeals for the D.C. Circuit upheld an earlier ruling from Chutkan that prevented the government from “forcibly — and irrevocably” transferring the man without allowing him to challenge his detention.

In a sign of the novel, significant questions raised by the case, the appeals court said in its ruling, “We know of no instance — in the history of the United States — in which the government has forcibly transferred an American citizen from one foreign country to another.”

The Pentagon said in its filing Thursday that it intends to release the man with the money and clothing he had when first detained, plus food and water to last several days and the new phone.

“DOD has taken all necessary and feasible precautions to ensure the safe release of the petitioner,” according to the affidavit from Defense Department official Mark E. Mitchell.

ACLU attorney Jonathan Hafetz said the government’s “meager offer to return his money and give him a cellphone does not remotely provide any protection from the violence and danger that exists throughout Syria.”

In asking for a temporary restraining order to block the release, the ACLU said in court papers that the man “does not oppose his release from U.S. custody. To the contrary, he is urgently seeking the restoration of his liberty. What he opposes is ‘release’ into an area of certain danger and possible death.”

The ACLU, noting the man’s citizenship, said in its in Thursday night filing that the government has not given him “any identification or indication of why the United States has placed him in this dangerous territory after nearly nine months of detention as an alleged ‘enemy combatant.’”

The government has said in court filings that the man was born in the United States but raised in Saudi Arabia. He attended college and studied electrical engineering in Louisiana, is married and has a 3-year-old daughter whom he tried to register as an American citizen on two trips to the United States in 2014, according to court filings.

Government filings show the man told the FBI that he worked for the Islamic State guarding a gas field and monitoring civilians.

He claimed that he was a freelance journalist who was arrested and agreed to work for ISIS to try to gain release, according to court records. The FBI said it could find no evidence of articles he wrote.

The ACLU said it is seeking the man’s release in a safe place, not a war zone, and not having him handed over as a prisoner to another government.

U.S. officials also plan to notify the allied Syrian Democratic Forces that the man will likely be traveling through checkpoints and that the United States does not seek his detention, said Mitchell, a principal deputy assistant secretary.

The filing includes assurances from the government that the group has committed to “respect human rights and the rule of law” and has acted consistently with those commitments.

In a statement Wednesday, the ACLU’s Hafetz noted that the State Department has issued “do not travel” warnings for Syria, advising U.S. citizens who ignore them to leave DNA samples and draft a will.

Spencer S. Hsu contributed to this report.