KABUL, Afghanistan—The residents of the Afghan capital, both native and foreign, are waiting for President Obama — to make up his mind.

The president’s lengthy review of Afghan policy — the results of which he’s finally expected to announce before Thanksgiving — has created a dangerous sense of drift here. “I think everyone would feel much better if we knew what we were doing,” one NATO officer told me. “What does the final American contribution to this effort look like? We have to lay this out. Everyone is waiting to respond to what we do.”

The absence of a clear U. S. policy — at a critical juncture when the Taliban is gaining — has fed Afghan conspiracy theories that America secretly supports the insurgents. Meanwhile, Obama’s delay has sapped domestic support for continued military engagement, which in turn fans Afghans’ fears that we will once again abandon their country.

The uncertainty about American intent also feeds the perception here that the Taliban is winning. It undercuts the will of European countries to stay on, even as the United Nations has pulled out hundreds of staffers after a bomb destroyed one of its guesthouses.

So if Obama is to regain lost momentum, it is essential that he lay out his decision with conviction, clarity and commitment. Psychology is key to this conflict: If Afghans and other governments in the region think the United States is eyeing the exit, the Taliban’s momentum will increase, as will the likelihood of chaos and civil war.

In the absence of a presidential decision, many Americans are confused about why we’re even in Afghanistan, especially since al-Qaida is based next door in Pakistan. The reasons are complex: to keep insurgents from precipitating the collapse or militant takeover of Afghanistan, with dire consequences for nuclear- armed Pakistan; and to buy time for the Afghan government to develop its own security forces.

In the meantime, the security burden will fall on international forces. The top U. S. commander in Afghanistan, Gen. Stanley McChrystal, reportedly believes 40,000 additional troops are needed to achieve those goals; a decision to send far fewer would signal to the region that Obama isn’t committed.

How would those troops be used? In the south, where the Taliban is strong, it’s hoped that the influx would clear out the Taliban and make it possible to pump in economic aid. The goal would be to link up small protected areas to form a larger zone that’s sufficiently stable and prosperous to show the population that there is an alternative to Taliban rule.

There are other possible ways to help Afghans undermine the Taliban, although none is a silver bullet. In some parts of the country, tribal militias may be encouraged to oppose the militants. In others, villages will produce local protection forces. A robust plan to reintegrate low-and mid-level Taliban into their communities also could undermine Taliban leaders.

Will any or all of these experiments work? I don’t know. But I do know that in Iraq, small successes led to glimmers of optimism that, in turn, created new opportunities. U. S. forces made their own luck in Iraq, and they hope to do so in Afghanistan.

Would more U. S. troops lead to a nationalist rejection of the foreign presence? As in Iraq, Afghans have an ambivalent relationship with foreign troops. They welcomed them initially, in 2001, but were disappointed that security got worse and the economy didn’t get better. If the Americans could finally show results, I think most Afghans would tolerate them for the time being; they don’t want the Taliban back.

As for corruption under President Hamid Karzai, there are ways to work around him. Remember when Iraqi Prime Minister Nouri al-Maliki’s central government was considered hopeless? That led U. S. officials to focus on bottom-up work at the provincial level. The same approach can be taken in Afghanistan.