The meeting comes amid speculation that the North may carry out a major provocation including an additional nuclear test. In the latest provocation, the North fired a ballistic missile from its eastern port of Sinpo into the East Sea.

China's top nuclear envoy may also deliver his country's opposition to the installation of the missile defense system, called the Terminal High Altitude Area Defense here.

Last year, South Korea decided to host the THAAD on its soil despite China's fierce opposition. Relations between them have since deteriorated as China launched retaliatory measures against South Korean companies and goods.

Less important in his trip to Seoul might be to have chances to meet presidential hopefuls, including leading presidential candidates -- Moon Jae-in of the largest Democratic Party and Ahn Cheol-soo of the center-left People's Party, diplomatic sources said.

The sources said that he is trying to meet all major presidential candidates. An embassy official said that nothing has yet to be confirmed in terms of his meetings with politicians.

His meetings with presidential candidates might be aimed at discussing key issues involving the two countries with the possible future leader of South Korea before the May 9 presidential election to fill the void left by the ouster of former president Park Geun-hye.

Last month, US nuclear envoy Joseph Yun came to Seoul and met with presidential candidates and campaign officials. Though the meetings were not disclosed, they reportedly discussed a wide range of diplomatic issues concerning the two countries. (Yonhap)