WASHINGTON (AP) — The Pentagon is considering several options to reduce the number of troops in Afghanistan, including one that would shift to a narrower counterterrorism mission, the top U.S. military officer told Congress on Wednesday.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, did not disclose any potential troop totals, but he agreed that leaving a minimal U.S. footprint in Afghanistan to battle terrorists is a potential move.

"We have multiple options, that's one of them," he said. The U.S. currently has about 13,000 troops in Afghanistan. About 5,000 of them are doing counterterrorism missions. The remainder are part of a broader NATO mission to train, advise and assist the Afghan security forces.

Defense Secretary Mark Esper, who testified alongside Milley, told the committee that the U.S. military must remain focused on the counterterrorism mission even as efforts are made to negotiate a peace deal with the Taliban.

"We have an important counter-terrorism mission in Afghanistan," he said. "That means we've got to make sure Afghanistan never becomes again a safe haven for terrorists that can strike the United States."

He said commanders have told him and Milley that the U.S. can reduce its presence in Afghanistan and still perform the counterterrorism mission.

"I'm interested in reducing our force presence," Esper said, so that some portion of the troops now based in Afghanistan can be reallocated to other parts of the world to bolster U.S. preparedness for potential conflict with China or Russia. Esper has said he is reviewing U.S. military missions worldwide to determine how many can be reallocated in that manner.

The top U.S. commander for Afghanistan, Gen. Scott Miller, was to brief members of Congress on the progress in the 18-year war during a closed session later Wednesday.