GUANTANAMO BAY NAVY BASE, Cuba -- A Sudanese terror camp trainer on Tuesday pleaded guilty to conspiring with al Qaeda in Afghanistan in the ’90s under a plea bargain that, military sources said, offered him an early shot at freedom by 2015 in exchange for testimony at future trials.

Noor Uthman Mohammed, in his early 40s, handed the Obama administration its third guilty plea in a row at the war court. He stood before a Navy judge in a traditional white Muslim gown and headdress and said he voluntarily admitted to charges of conspiracy and supporting terrorism when he sealed a secret plea agreement with a thumbprint last month.

This deal comes at a time when Congress has imposed stiff new rules on resettlements, trials and relocations of Guantánamo’s last 172 prisoners and raises a key question: Is the clearest path out of Guantánamo for little-known captives now to admit to being a war criminal?

“The path does seem to be to admit guilt to these war crimes,” said George Washington University law professor Mary Cheh, a Washington, D.C., city council member serving as an observer here this week.

Guilty pleas in exchange for short prison sentences, she added, also let the government “gloss over fundamental legal issues” still bedeviling the on-again, off-again trials at a time when the White House is seeking “an endgame” for Guantánamo. For example, what constitutes a war crime? Is punishing people for acts that weren’t a war crime at the time constitutional?

Noor admitted to being a weapons instructor and sometime operations manager of the Khaldan terror training camp along the Afghan-Pakistan tribal frontier border before the 9/11 attacks. His thumbprint sealed a now-secret narrative of what he did at the camp and in the company of an alleged arch-terrorist known as Abu Zubaydah, a document that could potentially be used at future trials.

Also under seal was how much time he would have to serve on a punitive cellblock as a war criminal. Military sources said his prison sentence ends by January 2015, provided he meets the conditions of the plea bargain, which include testimony at future trials.

The Pentagon’s chief war crimes prosecutor, Navy Capt. John F. Murphy, said Noor “was part of the apparatus of al Qaeda,” between 1996 and 2000 at Khaldan. The 9/11 Commission Report said three of the so-called “muscle hijackers” who took part in the Sept. 11, 2001, terror attacks trained at Khaldan.

Murphy called the guilty plea “another step in the justice that we are achieving in the commissions.’’

A five-to-15-member jury of senior U.S. military officers will be chosen Wednesday to hear about Noor’s crimes and deliberate a sentence of up to life in prison. The Pentagon would only use that sentence if its shorter than in the plea bargain — or if Noor breaks the agreement.

Yet to be seen is whether congressional restrictions on releases doom him to a longer stay, since Sudan is currently on the State Sponsors of Terror list.

Congress has put the brakes on Obama’s Guantánamo closure ambitions both by blocking prisoner releases and the use of Defense Department funds for trials on U.S. soil.

The president signed the restrictions into law last month.

Since then, the only captive to leave this remote Navy base was Afghan Awal Gul, 48, in a coffin.

The military says he dropped dead in the shower of a medium-security prison probably of a heart attack, after he worked out on an exercise machine.