The cost of the war in Iraq will reach $320 billion after the expected passage next month of an emergency spending bill currently before the Senate, and that total is likely to more than double before the war ends, the Congressional Research Service estimated this week.

The analysis, distributed to some members of Congress on Tuesday night, provides the most official cost estimate yet of a war whose price tag will rise by nearly 17 percent this year. Just last week, independent defense analysts looking only at Defense Department costs put the total at least $7 billion below the CRS figure.

Once the war spending bill is passed, military and diplomatic costs will have reached $101.8 billion this fiscal year, up from $87.3 billion in 2005, $77.3 billion in 2004 and $51 billion in 2003, the year of the invasion, congressional analysts said. Even if a gradual troop withdrawal begins this year, war costs in Iraq and Afghanistan are likely to rise by an additional $371 billion during the phaseout, the report said, citing a Congressional Budget Office study. When factoring in costs of the war in Afghanistan, the $811 billion total for both wars would have far exceeded the inflation-adjusted $549 billion cost of the Vietnam War.

"The costs are exceeding even the worst-case scenarios," said Rep. John M. Spratt Jr. (S.C.), the ranking Democrat on the House Budget Committee.