HERAT, Afghanistan (AP) — The head of NATO said Friday that Afghan security forces are dying in record numbers because they have assumed a leading role in the fight against Taliban insurgents as foreign forces shift from combat to training and support.

Figures this week show that more Afghan security forces — army and police — have been killed fighting so far this year than in all of last year, with the casualty rate up 6.5 percent. This year 4,634 have been killed in action, compared to 4,350 in 2013. By comparison, some 3,500 foreign forces, including at least 2,210 American soldiers, have been killed since the war began in 2001.

"The increase in casualties among the Afghan forces reflects that they are now in the lead," said NATO Secretary General Jens Stoltenberg, who is currently visiting Afghanistan.

NATO is set to conclude its combat mission in Afghanistan by the end of the year, more than 13 years after the U.S.-led invasion that toppled the Taliban following the Sept. 11 attacks. Some 12,000 U.S. and NATO troops will remain in a training and support capacity.

Stoltenberg is making his first visit to Afghanistan since taking over as the head of the alliance on Oct. 1. He met with Afghan President Ashraf Ghani on Thursday and on Friday flew to the eastern city of Herat to honor fallen troops at the Italian base, Camp Arena. Italy has lost 53 soldiers in Afghanistan.

Afghan forces, he said, "have already been in the lead and have had the main responsibility already for almost a year. So what we are doing next year is in a way to confirm and implement what has been in large parts of Afghanistan the reality already. And that's also why we have seen increasing numbers of casualties," he said.

"Of course we will, together with Afghans, review the structure and composition of the Afghan national security forces and do what we can to help them reduce the numbers of casualties."

NATO will provide $4.1 billion in annual funding to the Afghan defense forces, enabling them to "pay salaries, buy equipment, conduct training, all this aiming at both making them more capable, but of course reducing the number of casualties," Stoltenberg said.