A parliamentary committee has heard the budget for Australia's involvement in Iraq for this financial year has already blown out by $112 million.

The total amount of Federal Government money pumped into Australia's involvement in the Iraq war is expected to top $2.1 billion by the year 2010.

Despite combat troops being withdrawn from Iraq by June, the chief of the Australian Defence Force, Air Chief Marshall Angus Houston, says another $600 million has been allocated for the period until 2010.

"Which will bring the total from approved funding for Operation Catalyst for the period starting July 16, 2003 to $2158.7 million," he said.