The chief Pentagon prosecutor in the military trials of alleged al Qaeda fighters at Guantanamo Bay has requested that the presiding officer in the cases "closely evaluate" his impartiality and consider resigning, according to a document filed in the tribunal proceeding.

The prosecutor, Army Col. Robert L. Swann, suggested in the document filed Sept. 7 that in effect he accepted some arguments put forward by military defense lawyers last month that the presiding officer in the four cases, Army Col. Peter E. Brownback III, should consider stepping down.

In hearings last month at the U.S. Navy base at Guantanamo Bay, attorneys for the detainees argued that Brownback should quit because he is close friends with retired Army Maj. Gen. John D. Altenburg Jr., who oversees the military trials as the tribunals' "appointing authority."

The lawyers pointed out that Brownback and Altenburg have known each other since 1977, that Brownback's wife worked for Altenburg, and that Altenburg hosted Brownback's retirement party in 1999.

At preliminary hearings for detainees last month, defense attorneys asserted that the proceedings were stacked against the defendants and suggested that four others on the panel that will decide their guilt or innocence were also unqualified to serve. The lawyers' legal strategy, in part, is to get the prosecutions moved to U.S. criminal courts.

Swann's filing shows that the prosecutors are joining the defense in expressing unease about how the cases are proceeding, experts in military law said yesterday.

"This is quite a remarkable development," said Eugene R. Fidell, president of the nonprofit National Institute of Military Justice.

Attempts to reach Brownback through the Pentagon yesterday evening were unsuccessful.

Swann's filing asks that Brownback "closely evaluate his own suitability to serve as the presiding officer . . . with particular attention focused on whether his impartiality might reasonably be questioned." The prosecutor also asked Brownback to tell Altenburg "whether good cause exists for [Brownback's] removal."

Swann also wrote that he does not "object to the defense challenges for good cause" of three other military officers who are members of the military commission. In last month's hearings, defense attorneys had asked that four panelists be disqualified. One served in intelligence operations in the Middle East, another sent detainees from Afghanistan to Guantanamo Bay, a third commanded a Marine who perished in the World Trade Center attack, and a fourth said he could not with certainty detail the Geneva Conventions

Navy Lt. Cmdr. Charles Swift, who represents Yemeni detainee Salim Ahmed Hamdan, an alleged chauffeur for Osama bin Laden, said yesterday that "from the beginning, the [Pentagon] prosecutors have said, wait till we get there [to the tribunals] and you'll see how fair it all is. . . . In retrospect, they've realized it wasn't fair."

At the hearings last month, prosecutors said they had no objections to Brownback remaining in place.

Swift said the current arrangement is "incestuous" because Swann's supervisor is retired Air Force Brig. Gen. Thomas L. Hemingway, who is also counsel to Altenburg's office.