The U.S. special envoy for North Korea has said that while Washington was keeping all options on the table, he did not believe the United States was close to using military action to rein in Pyongyang's nuclear and missile ambitions.

"Our policy is very much for the peaceful resolution of the North Korean nuclear crisis. We've said over and over again that what we want to see is dialogue," Joseph Yun said at a news conference in Tokyo on Thursday evening.

"Having said that, we also have said ... that all options are on the table and by all options, it has to include military options," he said. "But ... I don't believe we are close to it."