WASHINGTON — The director of national intelligence, James R. Clapper Jr., described on Sunday his secret mission to seek the release of two Americans held in North Korea as a series of grim encounters with officials who expressed disappointment that he had not come bearing a “breakthrough” in relations.

“I was quite apprehensive because we weren’t sure how this was going to play out,” Mr. Clapper said on the CBS News program “Face the Nation,” offering a detailed description of the visit to Pyongyang, North Korea’s capital, this month. He said he had no certainty that the two Americans — Kenneth Bae and Matthew Todd Miller — would be freed until hours before he left North Korean soil.

Mr. Bae, 46, had been detained in 2012 after North Korea accused him of using a Christian youth group to plan a “religious coup d’état.” Mr. Miller, 25, was charged with unruly behavior after tearing up his visa this year in a reported attempt to get inside North Korea’s feared prison camps to write about them.

Mr. Clapper, a blunt-spoken retired general, had seemed an unusual choice for the mission, which would more commonly be handled by diplomats or even former presidents, like Bill Clinton and Jimmy Carter.