Mr Bosworth replaces Christopher Hill as the top US official on North Korea
The new US envoy on North Korea has arrived in Beijing for talks aimed at breathing life into the stalled disarmament deal with Pyongyang.
Stephen Bosworth will meet top Chinese officials to discuss how best to persuade North Korea to permanently abandon its nuclear ambitions.
His visit comes amid rising tension in the region over the communist state.
North Korea's neighbours believe it could be planning to test-fire a long-range missile.
It announced last month that it was preparing to launch a communications satellite, but some suspect this could be a cover for a test of the Taepodong 2 missile, capable of reaching Alaska.
On Tuesday, a report from Japan suggested it could send a destroyer carrying missile interceptor technology to the Sea of Japan (East Sea) in preparation for such an event.
Mr Bosworth, a former ambassador to South Korea, was appointed as the Obama administration's emissary on North Korea last month. He replaces Christopher Hill.
After China, he will move on to Tokyo and Seoul for more meetings.
US Secretary of State Hillary Clinton said last week that his visit to the region was to "move the six-party process forward".
North Korea agreed in February 2007 to abandon its nuclear programme in return for aid and diplomatic incentives, in a six-nation deal also involving the US, China, Russia, Japan and South Korea.
There has been some progress; last year, Pyongyang closed down its Yongbyon nuclear reactor.
But the talks are now deadlocked over the issue of how information it handed over about its weapons' programme is verified.
China's Foreign Ministry spokesman Qin Gang acknowledged that there were obstacles ahead.
"At present, there are some new and complicated circumstances in the six-party talks process, we hope these difficulties will be temporary," he said.
"We hope all the six parties are still bearing in mind the big picture of denuclearisation of the Korean peninsula and the peace and stability of East Asia."
Correspondents say Pyongyang's possible missile launch could be an attempt to grab the attention of the new US administration.
North Korea has issued a number of bellicose statements in recent days, the latest of which demands a joint US-South Korean military drill be called off.