South Korea's top nuclear envoy will visit China this week to coordinate policy towards North Korea amid high tensions on the Korean peninsula, his office said Tuesday.

Wi Sung-Lac will meet his Chinese counterpart Wu Dawei during a two-day trip to Beijing from Wednesday, the foreign ministry said.

Discussions are expected to focus on stalled nuclear disarmament talks and bitter cross-border relations, it said.

Six-party talks on ending the North's nuclear programmes in return for diplomatic and economic benefits have been stalled since December 2008.

The North fuelled regional security fears last November by disclosing an apparently functional uranium enrichment plant, which could give it a second way to make atomic bombs in addition to its plutonium stockpile.

The North has repeatedly expressed conditional willingness to return to the six-party forum it quit two years ago.

But icy ties with the South, following two deadly border incidents blamed on the North, are complicating efforts to revive the talks grouping the two Koreas, the United States, China, Russia and Japan.

China and other parties say the North should discuss its nuclear programme with the South as a prelude to full six-party talks.

Pyongyang said last week it would no longer deal with Seoul and threatened retaliation after South Korean troops had reportedly used its rulers as rifle-range targets.

Russia's deputy nuclear envoy Grigory Logvinov will visit Seoul on Thursday.

Kurt Campbell, US assistant secretary of state for East Asian and Pacific affairs, is to arrive in Seoul on Friday.