NATO defence ministers begin talks Thursday facing dilemmas after France abruptly decided to end its Afghan combat mission early and a leaked report accused Pakistan of secretly aiding the Taliban.

The French move is set to dominate two days of talks meant to review progress in the Afghan military transition, discuss ways to keep strong military capabilities in times of austerity and prepare a May summit in Chicago.

But allies will now also be confronted with a NATO report, leaked to British media and based on interrogations of detainees, claiming that Islamabad, via its ISI intelligence agency, is "intimately involved" with the insurgency.

President Nicolas Sarkozy announced last week that France would end its combat role in Afghanistan in 2013, a year early, after four French toops were killed by a renegade Afghan soldier.

He also encouraged all allies to do the same, but officials indicated that NATO would maintain a carefully crafted plan to hand Afghan forces full control of the battlefield by the end of 2014.

"We stick to the roadmap that was outlined at the NATO summit in Lisbon in November 2010," NATO chief Anders Fogh Rasmussen said on Monday.

British Prime Minister David Cameron cautioned against abrupt withdrawals.

"I don't want to see some sort of cliff edge in 2014 when all of the remaining troops come out at once," Cameron told reporters after talks Saturday with Afghan President Hamid Karzai.

With 130,000 foreign troops in Afghanistan, one senior NATO military official said changing the calendar would be a logistical headache, noting that there is $30 billion (22.8 billion euros) worth of military materiel in the mountainous, landlocked nation.

"Removing all the equipment and forces we have there will take a long while," the official told AFP on condition of anonymity.

The French decision revived fears that other allies, influenced by war-weary voters, would return home earlier.

"We are concerned there might be a rush to the exit with one important ally opting out of the (transition) timeframe," said an alliance diplomat. "The end of 2014 is realistic. This is the goal we should all aim for."

The report of Pakistani collusion with the Taliban will also cast a shadow over the meeting amid already tense relations with Islamabad.

NATO ties with Pakistan plunged to a new low after US air strikes killed 24 Pakistani soldiers along the porous Afghan border on November 26. Islamabad has since closed its border to NATO supply trucks.

"Pakistan's manipulation of the Taliban senior leadership continues unabatedly," the report, based interrogations of more than 4,000 captured Taliban and Al-Qaeda operatives, was quoted as saying by the BBC.

The debate on Afghanistan will likely continue at the Munich Security Conference from Friday to Sunday, an annual gathering of top officials and military experts from around the world in the German city.

In Munich, US Defence Secretary Leon Panetta will be joined Saturday by US Secretary of State Hillary Clinton and French Foreign Minister Alain Juppe for discussions on transatlantic relations and ties with Russia.

Former US secretary of state Henry Kissinger will then lead a debate on US, Europe and Asia with EU foreign policy chief Catherine Ashton, Australian Foreign Minister Kevin Rudd and US Senator John McCain.

"We don't want to make it a Chinese-American debate. We also want to see how Europe is viewed in Asia," said veteran German diplomat Wolfgang Ischinger, the event's chairman.

President Barack Obama is shifting US military attention to Asia and the Pentagon announced last week that it would withdraw two of its four army brigades from Europe in 2014.

Russian Foreign Minister Sergei Lavrov will join the talks in Munich amid tension between Moscow and NATO over Russian concerns that an anti-missile system could be aimed at Russia.