The U.S. military has hit as many as 17 separate targets connected to a shadowy al-Qaida cell in Syria known as the Khorasan group, U.S. officials say, as part of a little-discussed air campaign aimed at disrupting the group's capacity to plot attacks against Western aviation.

U.S. intelligence analysts disagree about whether the attacks have significantly diminished the group's capabilities, according to the officials, showing how difficult it has been to develop a clear picture of what is happening on the ground in Syria.

American officials briefed on the matter agree that the air attacks have forced militants into hiding and made their use of cellphones, email or other modern communications extremely risky. The officials spoke on condition of anonymity because they were not authorized to discuss classified assessments.

There is some disagreement about how much the airstrikes have undermined the group's ability to pose an imminent threat, U.S. officials say. Some U.S. officials say the military believes the strikes have lowered the threat, while the CIA and other intelligence agencies emphasize that the group remains as capable as ever of attacking the West.

The Khorasan group, as first reported in September by The Associated Press, is comprised of veteran al-Qaida operatives within the Nusra Front, the Syrian al-Qaida affiliate fighting the government of President Bashar Assad. Instead of battling Assad, Khorasan operatives are focused on planning attacks against the West, in part by fashioning nonmetallic bombs to place on airplanes and recruiting terrorists with Western passports who can slip past security, U.S. officials have said.

Intelligence about Khorasan group plotting led the Transportation Security Administration in July to ban uncharged electronic devices on certain flights originating in Europe, Africa and the Middle East.

The U.S. first attacked the group 10 days after the AP story, with dozens of Tomahawk missiles fired off U.S. Navy ships in the Persian Gulf and Red Sea targeting eight Khorasan sites.

Army Lt. Gen. William Mayville, director of operations for the Joint Chiefs of Staff, said at the time that the attacks were ordered because the group was "nearing the execution phase of an attack either in Europe or the homeland."

Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said they disrupted the group's plotting, but he did not know for how long. FBI Director James Comey said he believed the plots had not been stopped and that the Khorasan group's threat to the U.S. was undiminished. Other intelligence officials embraced Comey's view.

Since then, the U.S. military has disclosed six other sets of strikes against the group, most recently on March 8, when bombers struck "a large tactical unit and destroyed four buildings and three tents," the military said. A strike in late February hit a Khorasan headquarters.

It's unclear whether group leaders were killed in the strikes. American officials have not said who has been hit.

"Although coalition airstrikes have killed a number of senior Khorasan group members, the group almost certainly will maintain the intent to continue plotting against Western interests unless completely destroyed," Marine Lt. Gen. Vincent Stewart, the head of the Defense Intelligence Agency, told lawmakers on Feb. 20.

Two U.S. officials familiar with the military's view said they believe the strikes have affected the group and reduced the imminent threat of an attack. One reason, an official said: The absence of intelligence that would lead the U.S. to believe the Khorasan group is actively planning a strike, unlike the clear indications intelligence officials were seeing before the start of the bombing campaign last year.

U.S. officials familiar with assessments by civilian intelligence agencies do not dispute that, but they interpret it differently. As long as many of the key Khorasan figures remain alive, the threat is undiminished, the officials say, because the militants were sent to Syria for the specific reason of attacking the United States and Europe.

U.S. officials now believe that an important member of the group, David Drugeon, survived a November airstrike. The French-born Drugeon is believed to be knowledgeable about explosives, U.S. officials have said.

One U.S. official said Drugeon's bomb-making skills were nearly as worrisome as those of Ibrahim al-Asiri, a member of al-Qaida's Yemen affiliate who has built three nonmetallic devices that were smuggled onto U.S.-bound jet liners. None detonated.

Drugeon, a convert to Islam who's believed to be 24 years old, spent three years fighting in Afghanistan and Pakistan before coming to Syria in late 2012 or early 2013, U.S. officials have said.

Some experts believe the group is led by Muhsin al-Fadhli, a Kuwaiti long wanted by the U.S. government. He was reported killed in a September attack, but U.S. officials now say they are not sure whether he is dead or alive.