WASHINGTON — Al-Qaida is working more closely with the Taliban in Afghanistan, raising concern that the militant group could bolster the fight against Afghan government forces, a spokesman for the U.S.-NATO mission said Thursday.

"By themselves, we don't think that they pose a real threat, a real significant threat, to the government of Afghanistan," Brig. Gen. Charles Cleveland, a spokesman for the mission, told Pentagon reporters during a video conference from Kabul. "But because we think that al-Qaida is ... beginning to work more with Taliban, they can present a bit of an accelerant for the Taliban. They can provide capabilities and skills and those types of things."

Nearly 15 years after the U.S. invaded after 9/11 to root out al-Qaida and oust its host, the Taliban, Afghanistan remains a dangerous country. Last fall, the head of al-Qaida, Ayman al-Zawahiri, announced that he was backing the new leader of the Taliban, Mullah Akhtar Mansoor.

"Since that time, we have seen more interaction" between the two groups, Cleveland said.

He estimated that there were 100 to 300 members of al-Qaida in Afghanistan.

"Although they have been significantly diminished, they do have the ability to regenerate very quickly, and they still do have the ability to pose a threat," he said.

The U.S.-NATO coalition has around 13,000 international troops, including 9,800 Americans, in Afghanistan. They are focused on training and assisting Afghan forces as they take on the insurgency largely on their own. Around 3,000 of the U.S. troops are engaged in counterterrorism operations against the Taliban, al-Qaida and the Islamic State group.

The U.S. conducted just under 100 counterterrorism strikes against al-Qaida and ISIS militants in Afghanistan between the month of January and March 1. During April, there were just under 19 strikes, the majority against ISIS and a few against al-Qaida targets, he said.

He estimated that the strikes had reduced the number of ISIS operatives in Afghanistan to closer to 1,000, from earlier estimates of up to 3,000.