US Secretary of State John Kerry will push China to rein in North Korea’s nuclear ambitions, as he meets with officials in Beijing.
The visit follows North Korea’s claim that it had successfully tested a hydrogen bomb earlier this month.
Mr Kerry told reporters that Pyongyang was “a major challenge to global security”.
China is North Korea’s main diplomatic and economic ally, but Beijing has condemned Pyongyang’s nuclear test.
Mr Kerry also plans to discuss US concerns about China’s activities in the disputed South China Sea, and the tightening of political space for civil society in China.
He arrived in Beijing on Tuesday evening at the end of a tour where he also visited Laos and Cambodia.
Mr Kerry said he hoped that Wednesday’s talks with Chinese Foreign Minister Wang Yi and State Councillor Yang Jiechi would be “constructive and we will find a way forward”.
A senior US State Department official told reporters earlier this week that the “pre-eminent issue” for Mr Kerry was how China can convince North Korea to “reverse course” and roll back its nuclear and missile programme.
“The secretary has made no secret either to the Chinese or to you, the media, of his conviction that there is much more that China can do by way of applying leverage,” said the official, who added that the US hopes China would work with them, South Korea and Japan in doing so.
On Tuesday, Chinese foreign affairs ministry spokesman Hua Chunying told reporters that China had been making “unremitting efforts” on this issue, and that the US remarks were “unconstructive”.
She said denuclearisation had run into difficulties because of “some parties’ failure” to work in the same direction and urged the US to work with China “instead of pointing fingers and making inappropriate remarks”.
The State Department said Mr Kerry also plans to discuss Beijing’s “continuing tensions and problematic behaviour” in the South China Sea.
China, which has multiple competing claims with other countries in the resource-rich sea, has angered several neighbours by constructing artificial islands on claimed reefs, and building runways and other facilities on them.
The US has warned China to stop all construction, but Beijing insists that such activity is within its legal rights.
In Laos and Cambodia, Mr Kerry had called on the two countries, who are members of the Association of Southeast Asian Nations (Asean), to present a united front against China on the issue.
Laos is chairing Asean this year and, like Cambodia, shares a close economic relationship with China.
Ms Hua on Tuesday accused the US of “stirring troubles and sowing discord” over the matter, and urged it to work for peace and stability in Asia Pacific.