South Korea's top diplomat will go ahead with a plan to visit the United States this week to discuss North Korea's nuclear issue despite the announcement of her counterpart's dismissal, a foreign ministry official said Wednesday.

Foreign Minister Kang Kyung-wha is to leave for the US on Thursday for a three-day stay during which she plans to meet with Deputy Secretary of State John Sullivan, according to the official.

The go-ahead decision came after US President Donald Trump made a surprise announcement late Tuesday night to replace Secretary of State Rex Tillerson with Mike Pompeo, head of the Central Intelligence Agency.

Kang and Tillerson were supposed to meet on Friday (Washington time).

"The two sides shared a recognition that it is important to maintain firm coordination through close communications via diplomatic channels despite the personnel replacement," the official said on condition of anonymity.

Last week, the US proposed holding a summit with North Korea by May to discuss denuclearization. The meeting would be preceded by a summit that South and North Korea agreed to hold in late April.

Earlier in the day, Lee Do-hoon, South Korea's top nuclear envoy, left for Washington to discuss details of the planned back-to-back summits. (Yonhap)