(CNN) As many as 50,000 ISIS fighters have been killed since the war against the terror group began, a senior US military official told CNN.

The official called that figure a conservative estimate.

ISIS recruitment also has fallen off. It recruited only several hundred foreign fighters this year, compared with a couple thousand a month last year, CNN has learned.

In addition, the official also revealed Thursday that in May 2015, US special operations forces came "tantalizingly close" to capturing or killing ISIS leader Abu Bakr al Baghdadi in Raqqa, but failed to do so because classified information was leaked to the news media.

The official briefed reporters at the Pentagon on the condition his name not be used due to the sensitivity of the information.

The official noted that after the May 2015 raid in Syria that killed ISIS operative Abu Sayyaf and led to the capture of his wife, the US got valuable information on Baghdadi from the wife after two days of interrogation.

At the time, she told them "last week we were with Al Baghdadi in Raqqa," the official said. "We had been tracking them in Raqqa, so we went back frantically to try to figure out where he (Baghdadi) was in Raqqa."

But the official said communications that were being monitored dried up which the official blamed news stories that were published about intelligence learned from the raid.

The senior military official also disclosed that earlier this week when President Barack Obama visited the US military in Florida he privately spoke about the incoming Trump administration to General Joseph Votel, head of US Central Command, and General Tony Thomas, head of US Special Operations Command.

"He asked specifically are there things we could be doing as an administration" to assist a smooth transition on military issues such as fighting ISIS and counterterrorism, the official said. The official would not discuss Votel's answer but broadly noted that Thomas spoke about some changes to how special operations interact with the rest of the government.

The bulk of the meeting with reporters dealt with the issue of special operations taking a leading role in coordinating across the entire US government efforts to counter extremist threats against the US and coalition partners originating from overseas.

The matter has caused bureaucratic headaches inside the Pentagon and Congress over the question of whether special operations forces like Delta Force and Navy Seals will operate overseas more than they already do. The official insisted special operations have no new authorities to operate. But special operations forces will set up a new center to coordinate their operations with coalition forces and other government agencies at an "undisclosed location," the official said.

The official revealed for the last 18 months there has been a US military policy that airstrikes are only allowed against targets where 10 or less civilians might be killed.

In a related matter, special operations is also set to become the leading part of the military for "countering weapons of mass destruction," taking that role over from the US Strategic Command.

There is growing concern that North Korea is edging closer to being able to deploy a nuclear weapon. The official said the US believes it has the capability to mate a nuclear warhead, missile and delivery system.

"It's the threat that keeps me awake at night," the official said. The only issue holding the North Koreans off at this point appears to be they have not mastered the technology to make a weapon re-enter the earth's atmosphere to reach its target. All of this is leading to stepped up "contingency planning," to deal with North Korea's nuclear capability if it came to that, the official said.