A US marine who pleaded guilty to urinating on the corpse of a Taliban fighter in Afghanistan is likely be demoted one rank under a plea agreement.

Staff Sergeant Edward W Deptola admitted to multiple charges at a court-martial on Wednesday, including that of violating orders by desecrating remains and posing for photographs with the corpses.

Deptola and another marine were charged last year after a video surfaced showing four marines in full combat gear urinating on the bodies of three Afghans in July 2011.

In the video, one of the marines looked down at the bodies and said: "Have a good day, buddy."'

The New York native is married with two children, but military officials declined to give his age.

The sergeant admitted to the judge that he urinated on one of the three corpses and posed in the "trophy photographs".

Deptola said he failed to supervise the marines under him when the desecration began, even though he had been briefed that such behaviour violated a marine corps general order.

"I was in a position to stop it and I did not. ... I should have spoken up on the spot," he said.

When asked by the judge why he did it, Deptola replied, "I have no excuse, no reason, ma'am. ... It was not the correct way to handle a human casualty."

The judge said she would have sentenced him to six months confinement, a $5,000 fine, demotion to private and a bad-conduct discharge.

But she is bound by terms of the plea agreement the sergeant reached with military prosecutors. A general will review the sentence and could choose to lower it.

Source: Agencies