The North Atlantic Treaty Organization is expected to formalize at its Lisbon summit tomorrow a new timetable for the withdrawal of foreign troops from Afghanistan.

The beginning of the drawdown of the 100,000 U.S. troop surge is still 2011, in line with President Obama’s promise to the American people. But a new deadline is being set for the completion of the withdrawal in 2014 and a full transition to Afghan security forces. The significance of that date is that it takes us beyond the next U.S. presidential elections.

The Pentagon says 2014 is an “aspirational” date that could slip further depending on the situation on the ground. The NATO secretary-general, Anders Fogh Rasmussen, told NPR this morning that NATO forces will remain for “as long as it takes.”

I can see this posing a political problem for Obama because he must have hoped that by the time November 2012 came along, Afghanistan would be forgotten as a campaign issue. The war certainly didn’t figure in the midterms and indeed foreign policy in general did not influence the result in any way.

But a presidential election is different. Obama will be under pressure from the Democratic base to stick to a withdrawal timetable, which the administration insists will be based on conditions on the ground.

What are those conditions now? NATO says its forces have regained the initiative, but there are signs that even in previously quiet zones such as Herat in western Afghanistan, violence and crime are on the rise.

In the meantime, the U.S. is escalating its military might in the battle against the Taliban in the southwest. The Washington Post reported today that M1 Abrams tanks have been deployed for the first time in the nine-year war. Yet these are the same aggressive tactics that have drawn protests from President Hamid Karzai, who angered U.S. officials with a recent interview with the same paper in which he complained that support for the war was being eroded.

Obama will have the chance to talk to Karzai in Lisbon about the strategy, which includes reaching out to the Taliban leadership to reach a political solution. But the president will return to Washington with a domestic problem of selling to his party the pursuit of this war over the horizon of his first term in office.