The Iraq war could cost U.S. taxpayers between $202 billion and $406 billion more over the next 10 years, depending on how quickly U.S. force levels can be reduced, congressional budget experts said on Thursday.

The Congressional Budget Office offered two cost scenarios for the war, which it said so far has cost almost $300 billion.

If the number of U.S. troops in the Iraqi theater can be reduced to 140,000 next year from the current level of about 190,000 and all are withdrawn by the end of 2009, the CBO said military operations will cost another $166 billion in 2007-2016.

But if troop levels decline more slowly and remain at about 40,000 through 2016, the CBO said military operations will cost another $368 billion.

In addition, the CBO said U.S. funding for Iraqi security forces could total $15 billion over the next 10 years, and diplomatic and foreign aid could cost another $15 billion over that period.

Additional costs for veterans’ medical care, disability compensation and survivor benefits caused by the war in 2007-2016 would cost $6 billion if troops are withdrawn by the end of 2009. They would cost $8 billion if troops remain longer, the CBO said.

The war costs have far exceeded the $100 billion to $200 billion estimate that then- White House economic adviser Lawrence Lindsey offered before the war — a number quickly shot down by other White House officials as unrealistically high.

The CBO, Congress’ nonpartisan watchdog, said predicting costs of the war has been more difficult than usual because the Bush administration “has provided little detail on actual costs to date, making it hard to use past expenditures to predict future costs.”

Estimates based on standard models and cost factors have “been consistently less than the amounts requested by the administration for the war on terrorism,” the agency said.

© 2006 Reuters