The real U.S. debate on Iraq begins with congressional consideration of the military budget. The president has requested almost three quarters of a trillion dollars to fund the military through Sept. 30, 2008. More than $150 billion is earmarked for Iraq.

Bruce Ackerman is a professor of law and political science at Yale University (bruce.acker- man@yale.edu). David Wu represents Oregon's 1st District in Congress (www.house.gov/wu).

The United States has already spent $350 billion there, so the president's proposal pushes the costs for Iraq close to the half-trillion mark. At the same time, he is demanding a $100 billion reduction in health-care funding, falling most heavily on poor children, while he would maintain his $200 billion annual tax cut, channeled mostly to millionaires.

It is Congress' job to restore fiscal balance by placing an overall limit on Iraq war expenditures. Congress should limit this president to spending half a trillion dollars on the Iraq war -- and no more.

While he may not like the limit (we don't either, but for the opposite reason), the president would have no choice but to sign this ceiling to get short-term funding for his war.

In taking this step, Congress wouldn't be initiating a grand constitutional battle over the war powers of the president: It would be exerting its constitutional power of the purse and playing its traditional role as a check on another branch of government, rebalancing runaway programs that threaten to overwhelm our fiscal health and national priorities.

Limiting all future expenditures in Iraq to $150 billion, tops, can in no way harm American troops in the field. It responsibly carries out the will of the American people: that the president, with professional military advice, should be unwinding this war and planning a prudent departure for friendlier nearby countries or home.

"Fanaticism," George Santayana famously observed, "consists of redoubling your effort when you have forgotten your aim." There is nothing which sobers the mind more than a fixed budget.

Even the administration concedes that Congress has the constitutional power to cut off funds. The challenge is to use this power creatively to both protect the troops and require the president to end his war on his watch. The key point is to establish the principle that President Bush is responsible for leading America out of the impasse he has created.

A budget cap also would create a framework that would encourage Congress to focus on the big picture, rather than engage in constant criticism of particular strategic or military decisions. A half-trillion-dollar ceiling would assure that all troops would leave Iraq by inauguration day of 2009. But the proposal also would provide a framework to debate a more rapid redeployment: If Congress wanted a quicker termination, it would need only to impose a rider with the next appropriations bill that specified some smaller number (say, $450 billion) as the ceiling for this tragic misadventure.

This seems a more profitable focus than a series of debates over the next round of strategic maneuvering that will follow the president's "surge." Secretary of Defense Robert Gates already is making assurances that if the surge doesn't work, he is pondering Plan B. But Plan B is really Plan Q, or maybe Z. It is time to call this endless series of rationalizations to an end.

The "half-trillion-dollar solution" is a choice of the lesser evil. There are no good options left. The American people should know that things can get worse -- that, whether the United States leaves today or after a decade of urban ground combat, it is conceivable that the U.S. military may have to return if Iraq ever becomes a true threat to the world or immolates itself in genocide.

But for now, the U.S. government should end this war with a minimum of domestic name-calling, a maximum of motive and opportunity for the many peoples of Iraq to solve their own problems without killing each other and a focus on finishing the job in Afghanistan (the last known mailing address for Osama bin Laden). Moreover, setting a fixed budget would initiate the hard task of rebuilding America's foreign policy on its traditional bipartisan basis. By forcing President Bush to clean up the mess he has created, Congress would permit the next president and Congress to avoid yet another round of recrimination, and confront together the very real challenges ahead.