The focus on the 16,000-strong deployment in Afghanistan on the second day of the ministers' meeting in Brussels came against a backdrop of increased Taliban attacks and uncertainty over US strategy.

Washington has already unnerved allies by abruptly pulling US forces out of northern Syria this month, opening the way for NATO member Turkey to launch a disputed operation to crush the Kurdish militias it regards as "terrorists".

NATO Secretary General Jens Stoltenberg insisted at the start of Friday's ministerial meeting that the transatlantic alliance's commitment to Afghanistan remains "steadfast".

"We will continue to support the Afghan security forces as they fight international terrorism and create the conditions for peace," he said.

"But the Taliban have to make real concessions and show real willingness to reduce violence."

US President Donald Trump last month scuppered a secret summit with Taliban leaders and Afghan President Ashraf Ghani meant to consider a draft deal under which the US could withdraw its thousands of troops leading the NATO mission.

- China conference? -

China is now stepping into the void by inviting a Taliban delegation to an "intra-Afghan" conference in Beijing next Tuesday and Wednesday, a spokesman for the militants, Suhail Shaheen, told AFP this week.

The Taliban refuse to talk to the Afghan government, and Shaheen said any attendance by Afghan officials in Beijing would be on the understanding they were representing only themselves and were low-ranked.

Beijing has not confirmed the conference, but says it is "willing to facilitate" the Afghan peace process.

The United States has not reacted to the alleged Chinese move.

But the US State Department on Thursday urged restraint as Afghans wait for results from September 28 elections.

Preliminary results have been delayed for what Afghanistan's electoral authorities said were technical issues. The last polls in 2014 were marred by allegations of rigging.

Days ahead of the election, the Trump administration cut $160 million in direct funding to Afghan authorities, citing corruption.