Brendan Nelson, his defence minister, had said earlier that "energy security" was one of the main priorities behind his country's support for the war.
His remarks added weight to war protesters' arguments that the US-led invasion of Iraq in 2003 was amied at grabbing the country's oil supplies rather than a bid to counter the threat posed by Saddam Hussein's weapons of mass destruction, which later proved to be non-existent.
Nelson told the Australian Broadcasting Corporation that Australia's priorities were set out in a defence and security review being released on Thursday "and resource security is one of them".
He said: "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.
"It's extremely important that Australia take the view that it's in our interests, our security interests, to make sure that we leave the Middle East, and leave Iraq in particular, in a position of sustainable security."
Nelson also said it was important to support the "prestige" of the US and UK.
"We're also there to support our key ally - that's the United States of America - and we're there to ensure that we don't have terrorism driven from Iraq which would destabilise our own region," he said.
Howard sent 2,000 troops to support US and British forces in the invasion. The country now maintains about 1,500 troops in and around Iraq.