Washington: The US is planning to end its combat operations in Afghanistan by mid 2013 and would switch to a "train-and-assist" role, Defence Secretary Leon Panetta has said.

"Hopefully, by mid to the latter part of 2013, we'll be able to make a transition from a combat role to a training, advice and assist role, which is basically fulfilling what Lisbon was all about," Panetta told reporters.

Even as the transition came as a surprise to many, Panetta argued that this is in fact the fulfillment of the Lisbon strategy.

At the NATO summit in Lisbon last year, the alliance had agreed on a plan to bring all troops home from Afghanistan by 2014 after transitioning security responsibility to Afghan forces.

Last June, Obama ordered all 33,000 US surge troops home from Afghanistan by the middle of 2012.

"2014 then becomes a year of consolidating the transition and making sure that those gains are in fact held, so that we can move towards a more enduring presence beyond 2014," he said.

"Hopefully, we could reach a point in the latter part of 2013 that we could make the same kind of transition we made in Iraq, from a combat role to a train-and-assist role," he said.

"It doesn't mean that we're not going to be combat-ready. We will be, because we always have to be in order to defend ourselves. We are going to be largely transitioning to a support role for the Afghan army as they take over these different areas in the future," he said in response to a question.

"I think it's really important for all of the nations that are involved, the NATO nations, the ISAF nations, to stand by the Lisbon strategy. The Lisbon strategy basically said that we ultimately are in a process where we will withdraw our forces by the end of 2014. And I think we ought to stick with that," Panetta said.

The Defense Secretary said that no decision has been made with regard to the number of forces in Afghanistan after 2013.

"No decisions have been made with regards to, you know, the level of force that we'll have in 2013. Obviously, as you know, we're taking down our surge force and that will take place by the end of the fighting season in 2012," he said.

"But beyond that frankly, we haven't made any decisions. We know that, what I can say is that 2013 is a critical year, and therefore will demand that we have a strong presence there in order to make sure that the gains that we've made up to that point are continued," Panetta said.

"And in order to do that, we are going to have to continue to weaken the Taliban. We're going to have to continue to improve the Afghan Army's capabilities and their operations. We're going to continue to improve governance in the areas that we transit, and we're going to continue to maintain a pretty strong presence there in order to assure that those goals are achieved," Panetta said.