The death toll among Afghanistan’s security forces will not be sustainable, even with the stalemate in the fight against Taliban militants, according to the Pentagon’s pick to be the next head of US Central Command.

“Their losses have been very high. They are fighting hard, but their losses are not going to be sustainable unless we correct this problem,” Lt Gen Kenneth McKenzie said during a Senate armed services committee hearing.

The assessment comes as both western-backed security forces and the Taliban have pushed to gain momentum as the US has stepped up efforts to find a peaceful settlement to end the 17-year-long war in Afghanistan.

Afghan President Ashraf Ghani said last month that since 2015 more than 28,000 members of the Afghan security forces had been killed.

McKenzie said the US would have to work with Afghan forces to improve how they recruit, train and carry out missions.

He added that Afghan forces were not capable of securing the country without help from the nearly 14,000 US troops deployed there. “If we left precipitously right now, I do not believe they would be able to successfully defend their country,” McKenzie said.

He said he did not know how long it would take for Afghan forces to be self-sufficient and that the number of Taliban fighters was estimated at 60,000.

Donald Trump wants to end the conflict between Afghan security forces and the Taliban, who are fighting to drive out international forces and re-establish their version of strict Islamic law after their 2001 defeat.

McKenzie said he was unaware of any plans to significantly change the US military footprint in Afghanistan.

Recent attacks underscore the pressure on Afghanistan’s overstretched security forces, suffering from their highest-ever level of casualties, estimates from the Nato-led “Resolute Support” mission show.

The Kabul government no longer releases exact casualty figures, but officials say at least 500 men are being killed each month and hundreds more wounded, a tally many consider low.

In November dozens of elite commandos were among the casualties suffered by Afghan security forces as the Taliban claimed to have taken a district in Ghazni province.

US commanders have said they expect the Taliban to step up military efforts to better their position while they maintain contacts with US special envoy Zalmay Khalilzad, aimed at opening peace negotiations.