WASHINGTON -- If we were allied with an Iraqi government that, however weak, was truly national -- cross-confessional and dedicated to fighting a two-front war against Baathist insurgents and Shiite militias -- a surge of American troops, together with a change of counterinsurgency strategy, would have a good chance of succeeding. Unfortunately, the Iraqi political process has given us Nouri al-Maliki and his Shiite coalition.

Its beginning was inauspicious. Months of wrangling produced a coalition of the three major Shiite religious parties, including that of Moqtada al-Sadr. Given Maliki's legitimacy as the first democratically elected leader of Iraq, however, he was owed a grace period of, say, six months to show whether he could indeed act as a national leader.

By November, his six months were up and the verdict was clear: He could not. His government is hopelessly sectarian. It protects Sadr, as we saw dramatically when Maliki ordered the lifting of U.S. barricades set up around Sadr City in search of a notorious death squad leader. It is enmeshed with Iran, as we saw when Maliki's government forced us to release Iranian agents found in the compound of one of his coalition partners.

The Saddam hanging did not change anything, but it did illuminate the deeply sectarian nature of this government. If it were my choice, I would not ``surge'' American troops in defense of such a government. I would not trust it to deliver its promises. Lt. Gen. David Petraeus thinks otherwise. Petraeus, who will be leading our forces in Iraq, has not only served two and a half years there, but has also literally written the book on counterinsurgency. He believes that with an augmentation of U.S. troops, a change of tactics and the support of three additional Iraqi brigades, he can pacify Baghdad.

Petraeus wants to change the U.S. counterinsurgency strategy, at least in Baghdad, from simply hunting terrorists to securing neighborhoods. In other words, from search-and-destroy to stay-and-protect. He thinks that he can do this with only a modest increase of five American brigades.

I am confident that Petraeus knows what he's doing and that U.S. troops will acquit themselves admirably. I'm afraid the effort will fail, however, because the Maliki government will undermine it.

The administration view -- its hope -- is that, whatever Maliki's instincts, he can be forced to act in good faith by the prospect of the calamity that will befall him if he lets us down and we carry out our threat to leave. The problem with this logic is that it is contradicted by the president's simultaneous pledge not to leave ``before the job is done.''

In this high-stakes game of chess, what is missing is some intermediate move on our part -- some Plan B that Maliki believes Bush might actually carry out -- the threat of which will induce him to fully support us in this battle for Baghdad. He won't believe the Bush threat to abandon Iraq. He will believe a U.S. threat of an intermediate redeployment within Iraq that might prove fatal to him but not necessarily to the U.S. interest there.

We need to define that intermediate strategy. Right now there are only three policies on the table: (1) the surge, which a majority of Congress opposes, (2) the status quo, which everybody opposes, and (3) the abandonment of Iraq, which appears to be the default Democratic alternative.

What is missing is a fourth alternative, both as a threat to Maliki and as an actual fallback if the surge fails. The Pentagon should be working on a sustainable Plan B whose major element would be not so much a drawdown of troops as a drawdown of risk to our troops. If we had zero American casualties a day, there would be as little need to withdraw from Iraq as there is to withdraw from the Balkans.

We need to find a redeployment strategy that maintains as much latent American strength as possible, but with minimal exposure. We say to Maliki: you let us down and we dismantle the Green Zone, leave Baghdad and let you fend for yourself; we keep the airport and certain strategic bases in the area; we redeploy most of our forces to Kurdistan; we maintain a significant presence in Anbar province where we are having success in our one-front war against al-Qaeda and the Baathists. Then we watch. You can have your Baghdad civil war without us. We will be around to pick up the pieces as best we can.

This is not a great option, but fallbacks never are. It does have the virtue of being better than all the others, if the surge fails. It has the additional virtue of increasing the chances that the surge will succeed.