The U.S. government said it accidentally turned over a classified document about how it determines who are the most dangerous detainees in Afghanistan to the American Civil Liberties Union, and wants a federal judge to order the group to return it and not release it to the public, according to court papers.

The contested document is a form used by the military to record the findings and recommendations of Detainee Review Boards at its detention center near Bagram air base in Afghanistan. The review boards, composed of military officers, determine whether a detainee poses what the Pentagon calls an Enduring Security Threat, or EST, and the document contains the criteria for assessing detainees.

A senior Pentagon official, in declaration to the court filed Wednesday in New York, said release of the document “could have significant deleterious repercussions with respect to our diplomatic relationships with Afghanistan and various other countries.”

“EST criteria and determinations are not currently a topic in our sensitive bilateral discussions with other countries,” said the official, William K. Lietzau, who added that “revelation of EST criteria would likely complicate those discussions.” He provided no detail but said he could explain why in a private meeting with the judge, if requested.

The ACLU argues that the document was improperly classified as secret and the organization should be allowed to post it on its Web site, as it has with thousands of other Defense Department documents it has obtained through the Freedom of Information Act.

“There is nothing in the form that should not be made public,” said Hina Shamsi, director of the ACLU’s National Security Project, in an e-mail to a Justice Department lawyer that was filed with the court. “We propose that the best way forward is for DOD to move expeditiously to declassify the form.”

The ACLU brought the release of the document to the attention of the government on May 25, about two weeks after it got it from the Pentagon, among a trove of other documents handed over in response to a court order.

The Justice Department discussed the issue by phone with ACLU lawyers “but ultimately plaintiffs did not agree to return the document to DOD,” Jean-David Barnea, an assistant U.S. attorney in New York, told the court in a submission. He noted that in previous cases classified documents that were accidentally released were ordered returned to the government.

Lietzau, who is deputy assistant secretary of defense for rule of law and detainee policy, said in his declaration that if the EST criteria was revealed it “would allow detainees to engage in conduct and manipulation specifically intended to undermine this crucial evaluation and determination—an evaluation that pertains not to whether there is a legal basis to detain the individual but rather to the nature and extent of threat the individual poses.”

Lietzau said that could lead to the potential mistaken release of “highly dangerous” detainees, which “is likely to lead to violent consequences and operate to the detriment of future military operations, operational security and national security.”

Shamsi described Lietzau’s arguments as “scare-mongering.”

“I think it is indefensible that the government seeks suppression of the document on that basis,” she said. “There is nothing about the information in there that is not otherwise publicly the U.S. position. . . . We have concerns about criteria but nothing about the criteria would surprise anyone.”

“The better way to proceed is to litigate and have the court say it is not properly classified,” she said.

The ACLU has until July 29 to respond to the government’s filings.