Seoul: South Korea's chief nuclear envoy goes to China on Tuesday for talks over six-country nuclear talks on North Korea.

At the weekend, a US nuclear envoy returned from Pyongyang with documents detailing the North's weapons-grade plutonium programme.

Washington said this was an "important first step" in getting a full nuclear declaration.

North Korea is likely to make the declaration to China, host of the six-country talks, in the next two weeks, a South Korean official said.

A new round of the talks among the two Koreas, China, Japan, Russia and the United States is expected to take place in June, the official said.