The government has admitted the need to secure oil supplies is a factor in Australia's continued military involvement in Iraq. Defence Minister Brendan Nelson said today oil was a factor in Australia's contribution to the unpopular war, as "energy security" and stability in the Middle East would be crucial to the nation's future. Speaking ahead of a key foreign policy speech today by Prime Minister John Howard, Dr Nelson said defence was about protecting the economy as well as physical security, and it was important to support the "prestige" of the US and UK. "The defence update we're releasing today sets out many priorities for Australia's defence and security, and resource security is one of them," he told ABC radio. "The entire (Middle East) region is an important supplier of energy, oil in particular, to the rest of the world. "Australians and all of us need to think well what would happen if there were a premature withdrawal from Iraq?" Dr Nelson said the primary reason for Australian troops remaining in Iraq was to prevent violence between the Sunni and Shia population, and to bring stability to the region. "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. "For all of those reasons, one of which is energy security, it's extremely important that Australia take the view that it's in our interests ... to make sure we leave the Middle East and leave Iraq in particular in a position of sustainable security." Isolationism would not make Australia safer, he said. When Australia joined the US-led invasion force of Iraq in 2003, the government said it was primarily because Iraq had weapons of mass destruction that could pose a threat to the US and its allies.