The door to dialogue remains open for North Korea, the United States' top nuclear envoy says, assuaging rising concerns that Pyongyang's two missile launches this past week could derail denuclearisation efforts made so far.

Mr Stephen Biegun, who was in Seoul for talks when the North fired two ballistic missiles on Thursday, stressed the importance of maintaining communication and cooperation between Washington and Pyongyang during a meeting with South Korea's Foreign Minister Kang Kyung-wha yesterday.