The top U.S. general in Afghanistan said he is starting to consider how many of the roughly 10,000 U.S. troops deployed there might come home next year.

"Every day, we are assessing that," Army Gen. John Campbell said Tuesday in remarks at the Brookings Institution in Washington.

"I owe back to my senior leadership at the end of the fighting season [this fall] an assessment of where we are and where I think we go in the future, and based on that, we will make some decisions about where we are in 2016 and beyond," said Campbell, commander of U.S. Forces in Afghanistan and Operation Resolute Support, as the Afghanistan mission is known.

In March, President Obama said he would slow the pace of the troop withdrawal from Afghanistan. Initially the White House plan called for cutting the current force of 10,000 in half by 2016. But Obama backed away from that milestone and signaled some or all of those 10,000 might stay next year.

Plans call for ending the U.S. military mission by the close of 2016, shortly before Obama leaves the White House. The "combat mission" ended last year and the comparatively small force that remains is focused on advising and assisting the Afghan military as well as on limited counterterrorism operations.

Despite reports of successful attacks by Taliban insurgents in recent months, Campbell gave an upbeat assessment of the Afghan security forces and their ability to repel those attacks.

He cited familiar weaknesses for the Afghan forces: limited aviation capabilities, poor intelligence gathering and analysis skills, an unreliable logistics supply chain and ineffective management of rank-and-file troops.

But as the U.S. aims to wrap up its military mission in Afghanistan, Campbell said U.S. military trainers may have to accept that those weaknesses will not be entirely eliminated.

"Over time, we'll come to a point where we're going to say, 'That's the best we can do,' or, 'They're not going to get any farther than that,' or, 'I have six months left, I need to reprioritize and move advisers to something that's going to ... be more important in the long run,' " Campbell said.

Attrition is a key problem. The Afghan army loses about 4,000 soldiers a month, mainly because they don't return from leave.

"We've done a deep dive and said, 'Why are they leaving?' It's because you have young soldiers or police who are in Helmand (province) and they've been fighting for two or three years and they haven't had a break," Campbell said.

"When you are fighting all the time and when you need to take a break and you have no other way, then you go back home [on leave] and you don't come back."

Many military experts say the rise of the Islamic State in Iraq and Syria suggests the U.S. should ratchet up its commitment to Afghanistan and consider keeping thousands of American troops there beyond 2016.

Campbell offered no opinions on that issue but acknowledged that Afghanistan is not ready to stand on its own without some form of military or civilian support from the West.

"We started probably late on growing their air force, so we're going to be there for a while to continue to work hard on the air force," Campbell said.

"I really do think this is a strategic opportunity to have a country in that part of the world that wants to be part of the international community. ... But they're going to continue to need our support. They can't do it without the international community," Campbell said.