Securing oil supply is a key factor behind Australia's involvement in the US-led war in Iraq, the country has admitted.

Australia's Defence Minister Brendan Nelson said a review of the country's defence strategy concluded that maintaining 'resource security' in the Middle East was a priority.

The centre-left opposition Labour Party said the government's admission that the conflict was linked to oil contradicted its statements before the 2003 invasion.

Labour is seeking to withdraw Australia's troops from Iraq.

Australian Prime Minister John Howard has played down the comments.

Mr Howard also ended speculation that Australia would withdraw its troops from Iraq in the near future, saying they will stay until the Iraqi security forces no longer need their support.