Top U.S. intel official on whether ISIS, al Qaeda are teaming up

In a rare interview, Director of National Intelligence James Clapper talked to "Face the Nation" moderator Bob Schieffer about whether ISIS and al Qaeda have joined forces in Syria. It's the first time a senior intelligence official has commented on such reports.

Clapper doesn't think so.

"We don't see that," he said. "There have been tactical accommodations on the battlefield, on occasion, where local groups have united in the interest of a tactical objective, but broadly, I don't see those two uniting, at least yet."

Schieffer also asked about his recent trip to North Korea to bring home two Americans being held captive - Kenneth Bae and Matthew Todd Miller. Clapper remembers flying in after dark and not really knowing what to expect.

"[I was] quite apprehensive because we weren't sure about how this was going to play out. I personally wasn't completely confident ... that they would actually release our two citizens."

Asked if he sees relations with Pyongyang changing, Clapper said:

"I think that remains to be seen as to where do we go from here. ... Will this perhaps serve as a catalyst or stimulus for more dialogue? I hope so but I don't know."

CBS News will have a lot more of Clapper's interview Sunday on "Face the Nation."