Colonel James Schnelle was relieved of his command after telling his superiors he was "pulled over... by the Northern Territory Police for suspected driving under the influence" in the city of Darwin last month, a US Marine Corps spokesman told AFP.

Darwin Local Court was told Monday that Schnelle failed a random breath test in the early hours of September 30.

The Australian Broadcasting Corporation reported that Schnelle was driving home from a restaurant and bar in Darwin at the time.

"This is a man of very high character, he has no convictions anywhere in the world and has contributed immensely to society," the national broadcaster quoted Schnelle's lawyer as telling the court.

"The US Marines are going to deal with him very harshly," he said.

The decorated officer was fined Aus$500 (US$353) for medium-range drink-driving and had his driving licence suspended for six months, a court official told AFP.

No conviction was recorded, she said.

Some 1,587 Marines are currently serving a six-month deployment in Darwin in an annual arrangement between long-time defence allies Washington and Canberra.

The deployments, part of Washington's strategic "rebalance" to the Asia-Pacific, come as Beijing flexes its economic and military muscles in the region.

The Marine Corp spokesman said an investigation into Schnelle's case was initiated, and Lieutenant Colonel Jeramy Brady was appointed the new officer-in-charge for the duration of the current rotation.