The top US envoy to the United Nations will visit South Korea on Sunday for engagements to advance bilateral and trilateral cooperation on North Korean threats and other issues.

During her four-day stay in South Korea, Ambassador Linda Thomas-Greenfield plans to meet senior Seoul officials to discuss ways to step up cooperation in the UN Security Council.

The ambassador's visit comes after Russia last month vetoed the UN's annual renewal of an expert panel monitoring the North's compliance with international sanctions.

Absent the resolution, the panel's mandate is set to expire April 30, a termination that observers say could chip away at international efforts to curb evolving North Korean nuclear and missile threats.

Thomas-Greenfield is expected to discuss with Seoul officials measures to ensure the continued reporting of the North's weapons proliferation and sanctions evasion activities.

She will also travel to the Demilitarized Zone separating the two Koreas, meet young North Korean escapees and speak with students at Ewha Womans University, before heading to Japan on Wednesday.

It marks Thomas-Greenfield's first visit to Seoul, and the first trip by a US ambassador to the UN since 2016. (Yonhap)