|Stephen Bosworth's, left, regional tour includes visits to South Korea, China and Japan [AFP]
Stephen Bosworth, the US special envoy for North Korea policy, is in China to discuss attempts to convince Pyongyang to end its development of nuclear weapons and ease tense relations on the Korean peninsula.
Tensions between the two Koreas have been at their highest level in years after the North killed four South Koreans, including two civilians, when it shelled the disputed frontier island of Yeonpyeong in November.
In March, the South blamed Pyongyang for torpedoing one of its navy ships, killing 46 sailors. The North denied the charge.
Bosworth's visit to Beijing on Wednesday came a day after he travelled to South Korean to discuss the standoff between the two sides.
On Wednesday, Seoul quickly dismissed an offer from North Korea called for "unconditional and early" talks as insincere.
Pyongyang's offer cames just days after Lee Myung-bak, the South Korean president, vowed to boost his country's defenses but made clear the door was open for talks with North Korean.
"We are ready to meet anyone anytime and anywhere, letting bygones be bygones, if he or she is willing to go hands in hands with us,'' said a statement carried by the North's official Korean Central News Agency.
It added that history has shown that such confrontation only lead to "armed clash and war".
South Korea's unification ministry immediately rebuffed the offer.
"We don't consider it as a sincere dialogue offer," Lee Jong-joo, a ministry spokeswoman, said.
She said the North must first apologise for the two attacks last year and take "sincere" steps toward its nuclear disarmament.
Both Seoul and Pyongyang have given recent indications that peace talks are possible, even after weeks of warlike rhetoric and military drills by both countries.
On Tuesday, Bosworth held talks with Wi Sung-lac and Kim Sung-Hwan, South Korea's chief nuclear negotiator and foreign minister, respectively.
A US state department spokesperson said that Bosworth and the South Korean side had met to "assess the current situation regarding North Korea's nuclear development and future response".
South Korea had previously brushed aside the North's overtures for dialogue, saying it must be preceded by actions that show it was serious about abandoning aggression and sitting down for discussions.
North Korea has said it is willing to return to six-way nuclear disarmament talks, which had been stalled for more than two years after Pyongyang rejected inspections of its atomic facilities.
Six-way talks on disarmament-for-aid have been held with the North, South, US, Japan, China and Russia.
When asked on Wednesday whether the US was pressurising South Korea to restart the talks with the North, Bosworth said: "Never."
He gave no further comment on his meetings.
The US is seeking assurances that the North is genuine in its commitment to disarmament before talks resume.
Bosworth is set to visit Japan on Thursday for further consultations on North Korean issues.
The US envoy for nuclear talks with North Korea, Sung Kim, is accompanying Bosworth to Seoul and Beijing.