The United States said on Friday its policy towards North Korea had not changed after a senior U.S. official responsible for nuclear policy raised some eyebrows by saying Washington would be willing to engage in arms-control talks with Pyongyang.

Some experts argue that recognizing North Korea as a nuclear-armed state, something Pyongyang seeks, is a prerequisite for such talks.

There is also a growing possibility that North Korea might carry out a nuclear bomb test, the head of the United Nations’ International Atomic Energy Agency (IAEA) has said.

But Washington has long argued that the North Korean nuclear program is illegal and subject to United Nations sanctions.

Bonnie Jenkins, State Department under secretary for arms control, was asked at a Washington nuclear conference on Thursday at which point North Korea should be treated as an arms-control problem.

The UN nuclear chief has said that a new nuclear test explosion by North Korea “would be yet another confirmation of a program which is moving full steam ahead in a way that is incredibly concerning.”

Rafael Grossi said the International Atomic Energy Agency sees preparations for a seventh test but has no indication of whether an atomic blast is imminent.

North Korea has rejected US calls to return to talks. A seventh North Korean nuclear test would be further “confirmation of a programme which is moving full steam ahead in a way that is incredibly concerning," the head of the U.N. nuclear watchdog said on Thursday.