Defence Force Chief Angus Campbell revealed on Wednesday he was contacted about the allegations by an American senior official in March 2021.

The US defence attache in Canberra warned credible evidence of war crimes could trigger the Leahy Law.

The law prevents US armed forces from providing assistance to partner units or organisations that violated human rights with impunity.

The concerns related to a document known as the Brereton report, which investigated alleged war crimes by Australian troops between 2005 and 2016.

It found credible evidence of 39 murders of Afghan civilians and prisoners committed by or at the instruction of Australian soldiers.

Appearing before a Senate inquiry, General Campbell said one member of the Australian Defence Force was moved as a result of the Leahy Law concerns.

He said the person's position was "adjusted" based on whether legal issues may emerge.

General Campbell said the law had never been triggered against Australian defence organisations but there was "a precautionary period where we looked to our arrangements".

He said March 2022 marked "the conclusion of the issue".

The military chief initially told the committee he had not briefed the current or former defence ministers about the US concerns raised with him.

After checking his records, General Campbell later confirmed the former minister was informed.

Independent senator and former soldier Jacqui Lambie said the ministers and public should have been notified about the US concerns because it was also a "threat", which the general rejected.

"You have crossed the line," she told him.

A spokeswoman for Defence Minister Richard Marles confirmed he had not been briefed on the matter.

"The deputy prime minister is briefed on matters relating to his portfolio as they arise and as is appropriate," she told AAP.

"Given there are serious privacy issues, it would be inappropriate to comment further."

Australian Associated Press