Meeting in Brussels, NATO’s foreign ministers have reaffirmed their countries' commitment to Afghanistan's "long-term security and stability" despite mounting Afghan casualties in the 17-year conflict.

NATO Secretary-General Jens Stoltenberg made the comments following the two-day talks ending on December 5, the day after a top U.S. general said the death toll among Afghanistan's security forces will no longer be sustainable unless urgent measures are taken.

Stoltenberg told reporters that the allies were "concerned about the high number of casualties" but said the increase in violence could be a sign that things are about to change.

"Sometimes there is an uptick, an increase in violence because different parties try to gain the best possible position at the negotiating table. So it may actually become worse before it becomes better," he said.

NATO took the lead on international security efforts in Afghanistan in 2003, wound down combat operations in 2014, and is now mainly training and advising Afghan forces so that they can handle the country's security needs.

However, the Western-backed government’s security forces have struggled to counter attacks from the Taliban and other militant groups since the withdrawal of most NATO combat troops.

"They are fighting hard, but their losses are not going to be sustainable” unless measures are taken to "correct" recruiting and training issues, Lieutenant-General Kenneth McKenzie, who has been nominated to lead the U.S. military's Central Command that oversees wars in the Middle East and Afghanistan, said on December 4.

'Stalemated'

Speaking at a hearing before the Senate Armed Services Committee, McKenzie also said that the United States and its allies need to keep helping the Afghans recruit and train forces to battle the Taliban's estimated 60,000 fighters.

"If we left precipitously right now I do not believe they would be able to successfully defend their country," he said, adding that "the operational military situation is largely stalemated."

Some 14,000 U.S. soldiers are currently serving in Afghanistan, and McKenzie couldn't say how much longer the United States would remain in the country.

In October, Defense Secretary Jim Mattis said Afghan forces had more than 1,000 dead and wounded during August and September alone.

And Afghan President Ashraf Ghani last month said the death toll among Afghan security forces since 2015 was close to 29,000 -- a figure far higher than anything previously acknowledged.

With reporting by AP