The US spends more than $9 million ($NZ12.8m) a day fighting Islamic State and has poured $2.7 billion ($NZ3.8b) into the international coalition's bombing campaign.
The US has poured $2.7 billion into the international coalition's bombing campaign against IS. Photo: AFP
The coalition has been conducting air strikes in Iraq and Syria since last August.
The first breakdown of US costs, released by the Pentagon, show that two-thirds of the total bill has gone to the Air Force.
It came as Congress rejected legislation banning further spending.
The US House of Representative approved a $579 billion ($NZ826b) defence spending bill.
It rejected an amendment calling for a stop to cash going on the fight against IS unless Congress passed a new authorisation for the use of force.
This week, the White House announced another 450 advisers for Iraq, bringing the total military personnel to 3500.
But officials emphasise there are no combat troops and the US mission is to train local forces to do the fighting.
On Thursday, the top general in the US said the country's intervention in Iraq could extend further.
General Martin Dempsey, chairman of the Joint Chiefs of Staff, said the role of calling in air strikes, which would put troops nearer the front lines, remained a future option.
He also raised the possibility of establishing a network of US training hubs in northern Iraq.
-BBC