BRUSSELS – A U.S. proposal to step back from leading combat operations in Afghanistan by the middle of 2013 divided NATO on Thursday 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 that they had been blindsided by Defense Secretary Leon E. 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, a senior French diplomat said.

Removing all combat forces in 2013 would be a year ahead of schedule.