By Dan Griffiths
BBC News, Beijing
North Korea's Foreign Minister, Paek Nam-sun, is visiting Beijing amid diplomatic efforts to revive stalled six-nation nuclear talks.
This visit comes as Chinese officials say negotiations over North Korea's nuclear programme are facing serious difficulties.
Last September North Korea agreed to give up its nuclear ambitions in return for aid and security guarantees.
But discussions about implementing that agreement broke down in November.
There has been no progress since then.
Pyongyang has refused to talk until Washington lifts financial restrictions it imposed on the North for alleged illegal activities such as currency counterfeiting.
But last week the top US envoy to the negotiations ruled out ending sanctions or offering any other incentives to bring North Korea back to the negotiating table.
China is a major supplier of food and fuel to North Korea and is one of very few nations with any influence in Pyongyang. But previous attempts to get the talks back on track have all failed.