Mr Bush will use a prime-time television address on Friday (US time) to endorse the troop withdrawal recommendation that has been made by his top commander in Iraq.
But White House officials say the reduction of 30,000 troops will be made on the condition of continued security and political progress in Iraq.
The move will leave around 140,000 troops in Iraq, roughly the same number as before Mr Bush ordered the 'troop surge' strategy earlier this year.
Mr Bush is also expected to say he understands the deep concerns Americans have about Iraq and their desire to bring the troops home.
But he will stress that the US will not abandon Iraq.
Yesterday Foreign Affairs Minister Alexander Downer said Australian troops would continue to be deployed in Iraq for the foreseeable future.
Meanwhile US Democrats have rejected General Petraeus's strategy for Iraq, saying he was planning on keeping US troops in the country for at least the next decade.
"It sounds to me as if General Petraeus is presenting a plan for at least a 10-year, high-level US presence in Iraq," said Democratic House of Representatives Speaker Nancy Pelosi after talks with Mr Bush. © 2007 Australian Broadcasting Corporation
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