Lieutenant General Kenneth McKenzie has warned that unless recruiting and training improve, local forces will not overcome the current casualty rate. McKenzie has been nominated to lead US military's Central Command, which oversees the Afghan war.

Last month, Afghan President Ashraf Ghani said nearly 30,000 local forces had been killed since they took over responsibility for security in the war torn country from NATO in 2015 -- far more than previously acknowledged.

Speaking after talks with NATO ministers, Stoltenberg said the issue had been a priority when he visited Afghanistan recently with senior military leaders and steps were being taken to address the problem.

"I share the concern about the high casualty rates, but the consequence of that is not to reduce our presence but to make sure we provide support to enable them to increase their capabilities and their resilience even more," Stoltenberg told reporters in Brussels.

McKenzie told the US Senate Armed Services Committee at his nomination hearing Tuesday that Afghan forces were still unable to effectively withstand the Taliban, who have made steady gains in recent years and now number about 60,000 in Afghanistan.

But Afghan Foreign Minister Salahuddin Rabbani insisted that despite the losses, his country's forces' resolve and appetite for the fight remain undimmed.

"We do have casualties, but as far as the determination and resolve of the Afghan security forces is concerned, be assured they are very resilient in defending their territory and their people against terrorist attacks," he said.

- Killer blast -

With the conflict mired in stalemate 17 years after the US-led invasion in the wake of the 9/11 attacks ousted the Taliban from power, Western powers are stepping up efforts to push negotiations.

President Donald Trump and many US lawmakers are growing frustrated with a succession of generals promising that things may soon turn a corner and angered over the $45 billion or so America still pays annually for its involvement in Afghanistan.

After talks in Brussels, foreign ministers from countries taking part in NATO's Resolute Support mission renewed a call for direct talks between the Taliban and the government.

Last week, Ghani announced a 12-strong team for prospective talks but the optimism for peace has been tempered by continuing attacks, including a blast outside a British security firm in Kabul that killed 10 people last week.

Stoltenberg warned that as all sides seek to press their advantage on the battlefield in the run-up to talks, the security situation "may become worse before it becomes better".

NATO has around 16,000 troops in Afghanistan to train, advise and assist local forces.