Although the economy has supplanted the Iraq war as the main issue in the presidential elections, the war continues.

It still costs at least $2 billion a week, although no one really knows how much. How does one estimate the long-term costs of providing medical services to returning veterans with physical and psychological damage? There is also the cost of putting American forces and their equipment, worn down by nearly nine years of war in a harsh climate, back into fighting shape?

Although more than 4,100 Americans have been killed in Iraq, the rate of casualties has dropped, although that is no comfort to families who have lost men or women in the conflict.

One of the worst aspects of the Iraq war now is the fact that, even if Sen. Barack Obama wins the election and moves promptly to bring the war to an end, as he has promised, there will remain the miserable job of withdrawing 147,000 U.S. troops from Iraq.

I have seen the withdrawal of foreign forces from a hostile environment in Somalia. By 1994 the United Nations had decided that some 18,000 Pakistani, Indian, Egyptian, Zimbabwean and other forces there had outlived their usefulness: They were not going to achieve peace among Somalia's warring factions. Their continued presence in Somalia meant only that they would continue to cost the United Nations money as they increasingly would become a target for the Somalis.

The Somalis made it harder by insisting that the weapons that U.N. forces had brought into Somalia, including tanks, artillery and helicopters, were now their property and had to be left behind.

There was no reason to believe the Somalis would leave the U.N. troops alone as they withdrew unless effective force protection measures were put in place. Nor is there any reason to believe that some of the armed elements in Iraq will leave U.S. forces alone as they withdraw. The Iraqis want us gone, but many are unlikely to see any reason to let us depart in peace.

The line will run something like, "We need those weapons for our own army and police. We need all the buildings and gear as contributions to rebuilding the Iraq that you destroyed."

But please do not mistake this description of the difficulty the United States will encounter in withdrawing from Iraq as an argument for staying. Whether we are out under the timetable that Mr. Obama is putting forward or whether we stay "until victory" as Sen. John McCain is advocating, we will need to leave sometime. Iraq will not become Puerto Rico.

To withdraw 18,000 U.N. troops from Somalia took six months and a 5,000-man U.S. Marine force to bring about. If one looks at the question proportionately, the United States would have to "surge" by another 40,000 troops just to get our forces out of Iraq in one piece.

In the meantime, the United States and the Iraqi occupation government of Prime Minister Nouri al-Maliki continue to wrangle over an agreement that would make legal the continued presence of U.S. troops in Iraq. They are currently there under a U.N. Security Council resolution. It expires Dec. 31 and it is very unlikely that the Security Council would extend it or issue a new mandate. (Russia and China both hold veto power and Russia is still one cross bear over U.S. support of the Georgian government of Mikhail Saakashvili and the Bush administration's insistence on deploying parts of an intercontinental missile shield on Russia's border in Poland and the Czech Republic.)

Thus, if the United States wishes to maintain the pretense that Mr. Maliki's government is independent and that a formal agreement is necessary to keep U.S. troops in Iraq, the United States is obliged to continue to try to negotiate a status-of-forces treaty.

There are at least two bones of contention. The first is that the United States wants to assure that U.S. troops do not fall under the jurisdiction of Iraqi courts for crimes they might commit, on duty or off duty. This does not necessarily relate to bombing villages or accidentally killing civilians. As has become an issue in Japan, it also can apply to charges of rape or murder against U.S. soldiers off duty.

Iraqi opposition to that part of the proposed agreement turns on the question of sovereignty. Some of the Iraqis can live with the idea that whatever U.S. soldiers do on duty is done in pursuit of military combat, but most of them can't stomach the idea of U.S. soldier impunity under Iraqi law while carousing.

Iraqis also want an unconditional commitment by the United States to withdraw its troops by a set date. One version has the United States out by 2012. Another has weasel-like language to the effect that U.S. troops will leave, unless conditions suggest otherwise.

Iraqi cleric Moqtada al-Sadr turned out an estimated one million Shiites in the streets of Baghdad last weekend calling for the United States to agree to a total withdrawal of its forces, as soon as possible.

The impact of this impasse on the Iraqi side is multiplied by the fact that elections are now scheduled there for January. No one -- least of all Mr. Maliki -- wants to take on Mr. Sadr and his people. And then there is the outcome of the upcoming U.S. elections, which Iraqis are watching closely.

The U.S. elections in November and Iraqi elections in January make the Dec. 31 deadline unlikely to be met, with no party, including the U.N. Security Council, likely to cut anyone a break at this point. My guess is that the Security Council would extend the mandate if Mr. Obama won, knowing he would seek to withdraw U.S. troops at a steady rate. If Mr. McCain won, it wouldn't, and my guess is that he would simply ignore the question of the legality of a continued U.S. presence in Iraq and stay with no international cover, a great start for a new administration.