BRUSSELS • A U.S. proposal to step back from leading combat operations in Afghanistan by the middle of 2013 divided NATO last week as some allies objected to being caught by surprise, and France suggested that the alliance completely end its involvement in fighting over the next two years.

Germany, Britain and other NATO members complained in closed talks at alliance headquarters here that they had been blindsided by Defense Secretary Leon Panetta, who described the U.S. plan to reporters on his way to Brussels on Wednesday, according to a senior NATO diplomat.

European governments, after backing the unpopular Afghan war for years despite little public support, said the U.S. plan was being viewed in news reports as an indication that Washington was eager to leave Afghanistan, which would make it harder for them politically to keep their own troops there, the diplomat said.

Reflecting those concerns, officials confirmed that France intended to pull its 2,500 remaining combat troops from Afghanistan by the end of 2013, and they suggested that the rest of the alliance consider whether to do the same, according to a senior French diplomat.

Removing all combat forces in 2013 would be a year ahead of schedule, but French officials say the faster timetable would help the alliance extricate itself from the decade-old war. "We must not leave the most difficult tasks for the end," French Defense Minister Gerard Longuet said in an interview.

U.S. officials favor handing over lead responsibility for fighting the insurgency to the Afghans next year, but keeping U.S. and allied combat troops there until the end of 2014.

U.S. officials insisted that the transfer of duties to the Afghans did not mean the U.S. would cease combat operations entirely, but several U.S. and NATO officials initially had trouble explaining what the change would mean in practice. The announcement also seemed to spook both Afghan officials and U.S. military commanders, who worried that it meant U.S. troops would be pulled out more quickly than expected — an impression that, despite multiple efforts, U.S. officials did not entirely dispel.

A senior NATO official briefing reporters explained the U.S. plan this way: Panetta 'said that the combat role will come to an end. But he also said that combat will continue, and that's exactly what I am saying."

The U.S. plan also seemed to rattle NATO Secretary-General Anders Fogh Rasmussen. He said Thursday morning that Afghan army and police personnel would be in the lead "by mid-2013," as Panetta had said, but at an evening news conference he said he needed to "clarify a few issues."

Apparently concerned that the U.S. announcement would lead other members of the alliance to withdraw their troops next year, Rasmussen pulled back from his earlier statement that Afghan troops would assume security responsibility throughout the country in 2013, with NATO taking a support role.

"It may be 2013. We don't know yet. It depends on the situation on the ground," he said.

Panetta offered reassurance that U.S. forces would still engage in combat even after the Afghan army takes the lead role next year. "Everyone understands that there's going to be a transition here," Panetta said after a day of meetings at NATO headquarters. "The Afghans will be in the lead, and we will continue to provide support."

Panetta said U.S. forces would train and advise Afghan units, conduct special-operations raids and be available to assist other troops in emergencies. He said they would only "engage in combat operations as necessary," a major shift away from the U.S.-dominated approach of the last decade.