About 550 Australian combat troops have been based in southern Iraq

Troops had turned over responsibility for security in two provinces to Iraqi forces and were no longer needed, Air Chief Marshal Angus Houston said.

"We have achieved our objectives in southern Iraq," he told a Senate committee. "It's time to leave."

New Prime Minister Kevin Rudd has promised to withdraw combat troops from Iraq by mid-2008.

'Very confident'

Australian military personnel have been deployed in Iraq since the US-led invasion in 2003.

About 550 combat troops remain in the country, plus another 1,000 personnel engaged in operations related to Iraq.

The combat troops have been based in the two southern provinces of Al-Muthanna and Dhi Qar.

But responsibility for security had been returned to Iraqi forces two years ago and they were no longer in need of Australian back-up, Air Chief Marshal Houston said.

"The conditions on the ground have been established whereby we can leave them to it and... we are very confident in their ability to handle the circumstances in those two provinces," he said.

The military chief described the outcome as "very pleasing". He said the move to pull troops out would likely have come even without the recent change of government.

Australian troops at air bases outside Iraq and on a warship guarding Iraq's offshore oil terminals will remain in place, as well as a 110-strong security team in Baghdad.

US Defense Secretary Robert Gates in due in Canberra at the weekend to discuss the Australian withdrawal and other military issues.