NATO sought to reassure Afghans Monday that despite talk of an early end to combat missions, foreign troops would fight "shoulder to shoulder" with local soldiers whenever needed until the end of 2014.

The reassurance came after confusion over remarks by US Defence Secretary Leon Panetta suggesting that Washington wanted to shift from a combat role to a "train and advise and assist role" by the end of 2013.

Defence ministers meeting in Brussels last week were, however, completely committed to the strategy already in place, a spokesman for NATO's senior civilian representative in Afghanistan, Simon Gass, told a news conference.

"And what that means is that right up until the end of the transition process, the end of 2014, NATO troops will be continuing to conduct combat missions wherever they are needed, shoulder to shoulder with Afghan troops."

Panetta, seeking to clear up any confusion, told reporters in Brussels that NATO troops "will have to be fully combat-ready" and will fight "as necessary" even as Afghan forces assume the security lead.

"We hope that the Afghan security forces will be ready to take the combat lead in all of Afghanistan some time in 2013," the Pentagon chief said, adding that the final plan will be decided by NATO leaders at a Chicago summit in May.

NATO spokesman Dominic Medley told the Kabul news conference that the capability of the Afghan security forces was growing quickly throughout the country -- "and that is why the transition is proving to be a success".

NATO has some 130,000 soldiers in Afghanistan fighting an insurgency by the hardline Islamist Taliban, but is training Afghan forces to take responsibility for security by the end of 2014 when it plans to pull out its combat troops.

"By the end of the year, we will have 352,000 members of the Afghan security forces," the spokesman for NATO's International Security Assistance Mission (ISAF), Brigadier-General Carsten Jacobson told the news conference.

"We are focusing on the training of the Afghan forces in order to be capable, sustainable and affordable," he said.

Despite NATO assurances that insurgents are on the back foot, a leaked secret NATO document, based on thousands of detainee interrogations, showed the Taliban believe they can reconquer Afghanistan once Western forces are gone.