WASHINGTON — The boost in troop levels in Iraq has increased the cost of war there and in Afghanistan to $12 billion a month, and the total for Iraq alone is nearing a half-trillion dollars, congressional analysts say.

All told, Congress has appropriated $610 billion in war-related money since the September 11, 2001, assaults, roughly the same as the war in Vietnam. Iraq alone has cost $450 billion.

The figures come from the nonpartisan Congressional Research Service, which provides research and analysis to lawmakers.

For the 2007 budget year, CRS says, the $166 billion appropriated to the Pentagon represents a 40% increase over 2006. The Vietnam War, after accounting for inflation, cost taxpayers $650 billion, according to separate CRS estimates.

The $12 billion a month “burn rate” includes $10 billion for Iraq and almost $2 billion for Afghanistan, plus other minor costs. That’s higher than Pentagon estimates earlier this year of $10 billion a month for both operations. Two years ago, the average monthly cost was about $8 billion.

Among the reasons for the higher costs is the cost of repairing and replacing equipment worn out in harsh conditions or destroyed in combat. But the estimates call into question the Pentagon’s estimate that the increase in troop strength and intensifying pace of operations in Baghdad and Anbar province would cost only $5.6 billion through the end of September. If Congress approves President Bush’s pending request for another $147 billion for the budget year starting October 1, the total bill for the war on terror since September 11 would reach more than three-fourths of a trillion dollars, with appropriations for Iraq reaching $567 billion.

Also, if the increase in war tempo continues beyond September, the Pentagon’s request “would presumably be inadequate,” CRS said.

The latest estimates come as support for the war in Iraq among Mr. Bush’s GOP allies in Congress is beginning to erode. Senior Republicans such as Senator Domenici of New Mexico and Senator Lugar of Indiana have called for a shift in strategy in Iraq and a battle over funding the war will resume in September, when Democrats in Congress begin work on a funding bill for the war.

Congress approved $99 billion in war funding in May after a protracted battle and a Bush veto of an earlier measure over Democrats’ attempt to set a timeline for withdrawing American combat troops from Iraq.

The report faults the Pentagon for using the Iraq war as a pretext for boosting the Pentagon’s nonwar budget by costs such as procurement, increasing the size of the military and procurement of replacement aircraft as war-related items.