Afghanistan

President Obama will soon make critical choices on Afghanistan, including how fast to withdraw 66,000 American troops and whether to keep a small residual force there once the NATO combat mission concludes at the end of 2014. His talks with the Afghan president, Hamid Karzai, this week will be an important marker in that process.

A lot has happened since the two men met in Kabul last May and signed a strategic partnership agreement. Some developments, like signs of an incipient peace process between the Taliban and the Afghan government, are promising. But many are not. The Afghan Army and police forces have taken responsibility for securing larger and larger swaths of the country, but the Pentagon has admitted that only 1 of 23 NATO-trained brigades can operate without American assistance. The recent alarming rise in fatal attacks by Afghan forces on their American military mentors has crushed whatever was left of America’s appetite for the costly conflict.

Ideally, the 66,000 American troops would already be leaving, and all of them would be out as soon as safely possible; by our estimate, that would be the end of this year. The war that started after Sept. 11, 2001, would be over and securing the country would be up to Afghanistan’s 350,000-member security force, including the army and police, which the United States has spent $39 billion to train and equip over a decade.

But there is a conflict between the ideal and the political reality. Mr. Obama has yet to decide how fast he will withdraw the remaining troops, and the longer he delays, the more he enables military commanders who inevitably want to keep the maximum number of troops in Afghanistan for the maximum amount of time. Another matter of concern is that Mr. Obama is seriously considering keeping a residual military force for an indefinite period after 2014. He needs to think carefully about what its mission would be and make his case to the public. Gen. John Allen, the commander in Afghanistan, had provided the White House with options for an enduring presence that went as high as 20,000 troops. That was an alarmingly big number, but fortunately now seems to be a nonstarter. American officials on Saturday said the administration is considering a much smaller force of 3,000 to 9,000.

If Mr. Obama cannot find a way to go to zero troops, he should approve only the minimum number needed, of mostly Special Operations commandos, to hunt down insurgents and serve as a deterrent against the Taliban retaking Kabul and Al Qaeda re-establishing a safe haven in Afghanistan. Mr. Obama will want to discuss all these issues with Mr. Karzai. The United States cannot go forward if Afghanistan opposes a residual force or puts undue restrictions on those troops.

Mr. Karzai, a deeply flawed leader who is expected to leave office next year, has his own agenda, which includes requests for updated American aircraft, surveillance equipment and longer-range artillery to modernize his army. Those requests cannot be taken seriously when Afghan security forces are increasingly murdering Americans and the Afghan government remains so profoundly corrupt.