NATO allies will Thursday discuss US plans to end combat operations in Afghanistan in 2013 and switch to a training mission before handing security control to Afghan forces by the end of 2014.

US Defence Secretary Leon Panetta set out the goal as he flew to Brussels for two days of talks with NATO counterparts that will also focus on how to maintain the strength of the allies' armed forces despite budget cuts.

"Hopefully by the mid-to-latter part of 2013, we'll be able to make a transition from a combat role to a train and advise and assist role," Panetta told reporters aboard his plane.

NATO leaders agreed at a summit in Lisbon in November 2010 to gradually hand over security responsibility to Afghan forces, with the goal of leaving them in full control by the end of 2014.

Panetta's comments were the first time the US administration had forecast American and allied troops could end their combat operations by the second half of next year.

He said Washington wanted to see all the NATO allies "respect" the alliance's timeline.

"We all went in here together and we'll all go out together, but we have to do it on the basis of a strong alliance and a strong commitment that was made in Lisbon."

French President Nicolas Sarkozy had appeared to upend the pullout strategy last week when he announced France would withdraw combat forces a year early, in 2013, after four unarmed French troops were killed by a renegade Afghan soldier.

But a senior US defence official said it was possible that there was no serious gap between the French stance and NATO's timeline, depending on the precise details of what Paris planned.

A diplomat said French Defence Minister Gerard Longuet "will try to clarify" the decision and "reassure allies that France does not intend to abandon them."

Longuet is expected to tell his counterparts that a number of French soldiers would stay beyond 2013 to continue the training mission.

Sarkozy and US President Barack Obama both face presidential elections this year, and war-weary voters could welcome signals that NATO troops, currently numbering 130,000, will finally come home after a decade of fighting.

The Pentagon chief's remarks represented the strongest signal yet that the White House wants to wrap up the wars it inherited from the previous administration, after having overseen the withdrawal of American forces from Iraq in December.

Obama took a similar approach in Iraq before the pullout there, declaring an end to the combat mission while the Pentagon renamed units as "advise and assist" brigades.

Despite the goal of ending the combat mission next year, the United States had no plans to move up the 2014 deadline for the withdrawal of American and coalition forces, Panetta said.

The NATO alliance had agreed on the 2014 timeline "and I think we ought to stick with that," he said.

Despite assurances from NATO that insurgents are on the back foot, a leaked secret NATO document showed Tuesday that the Taliban are confident they can reconquer the country once Western forces leave Afghanistan.

NATO spokeswoman Oana Lungescu downplayed the impact of the report, saying the Taliban "have suffered tremendous setbacks on the battlefield in the last year" and "lost a lot of ground."

Panetta said a future training force could include a counter-terrorism mission to strike extremists, along with standard training efforts.

He said 2013 would be a "crucial" year for the final transfer of remaining areas to Afghan security forces and "2014 becomes a year of consolidating the transition."

It was unclear how the planned shift from combat to a mainly advisory role would affect US troop levels.

With nearly 90,000 US troops now in Afghanistan, Panetta said "no decision has been made with regards to the level of forces we'll have in 2013."

By the end of September, the number of US troops is due to drop to 68,000, following the scheduled withdrawal of a "surge force" that deployed in 2010.

NATO members will also use Thursday's talks to prepare for a meeting of the alliance in Chicago in May.

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