The agency said average monthly spending on the war in Iraq may rise to eight billion dollars this fiscal year, up from 6.4 billion dollars a month in 2005.
It said the Department of Defense's annual war funding rose from about 73 billion dollars in fiscal 2004 to 102 billion dollars in fiscal 2005, "and may reach 118 billion in FY 2006 if the pending supplemental is enacted," the report said.
The report was issued shortly before Congress approved a 94.5 billion dollar emergency spending bill that included 65.8 billion dollars to fund military operations in Iraq and Afghanistan.
The CRS said 437 billion dollars have been appropriated since the September 11, 2001 attacks to fund US military operations in Iraq, Afghanistan, the broader war on terrorism and homeland defense.
Spending on Afghanistan averaged 1.3 billion dollars a month in 2005 and may rise to 1.5 billion in 2006, the report said.
The Congressional Budget Office estimates that "war costs could total 371 billion dollars between FY 2007 and FY2016," it said.
That would assume a drawdown of US troops engaged in those operations from about 258,000 currently to 74,000 by fiscal year 2010, it said.
"Adding that amount to the 437 billion dollars with the FY2006 supplemental (budget request), total funding for Iraq and the GWOT (Global War on Terrorism) could reach 808 billion dollars by 2016," the report said.