Australian troops aboard an armoured personnel vehicle pass by a checkpoint guarded by an Iraqi policeman at a junction near the Australian embassy in Baghdad (File)

Australia has admitted for the first time that securing oil supplies has been a key factor behind its involvement in the U.S.-led war in Iraq. Defense Minister Brendan Nelson says maintaining what he calls "resource security" in the Middle East is a priority for Australia, which still has about 1,500 troops in the region. From Sydney, Phil Mercer reports.

Releasing the government's review of its national security policy, the defense minister acknowledged that the supply of oil has influenced strategic planning.

"The defense update we're releasing today sets out many priorities for Australia's defense and security, and resource security is one of them, and obviously the Middle East itself, not only Iraq, but the entire region, is an important supplier of energy, oil in particular, to the rest of the world," he said.

Nelson says that, although energy concerns are important, the main reason Australian troops are still in the Gulf is to ensure that the humanitarian crisis in the region does not get worse.

Critics have accused the Australian government of telling lies about Iraq.

The main opposition Labor party says that, back in 2003, Prime Minister John Howard insisted the campaign to oust former Iraqi president Saddam Hussein had nothing to do with oil. It has chastised Mr. Howard for making up his policy in the Gulf as he goes along. Labor has promised to pull Australian troops out of Iraq if it wins national elections due later this year.

Anti-war protesters say the invasion of Iraq was more of a grab for oil rather than a genuine attempt to uncover weapons of mass destruction as the government has insisted.

Ministers in Canberra have brushed aside the criticism. They say they remain committed to helping the United States stabilize Iraq and combat terrorism. They also stress that there will be no "premature withdrawal" of Australian forces from the region.