BEIJING >> U.S. Secretary of State John Kerry is in Beijing to push Chinese officials to do more to rein in North Korea’s nuclear activities and decrease tensions over disputed parts of the South China Sea.

Wrapping up an eight-day, around-the-world diplomatic mission Wednesday, Kerry was meeting with senior Chinese officials to press them to take a firmer stance in urging North Korea to end its nuclear testing. China is North Korea’s main link to the outside world, and American officials say Beijing isn’t doing enough to persuade North Korea to stop the tests and return to disarmament talks.

The so-called six-party talks between the North and South Korea, the United States, China, Russia and Japan have been stalled since they were last held in December 2008. Pyongyang has since conducted three nuclear tests, including the latest on Jan. 6, sparking worries the country has made progress in its bomb program.

Kerry, who is meeting with Chinese Foreign Minister Wang Yi, State Councilor Yang Jiechi and President Xi Jinping, will also be calling for China to halt land reclamation and construction in disputed areas of the South China Sea, which have alarmed its smaller neighbors.

Kerry arrived in China from stops in Laos and Cambodia, where he called on the two members of the Association of Southeast Asian Nations to present a united front in dealing with increasing Chinese assertiveness over the South China Sea claims. His visits to Vientiane and Phnom Penh come ahead of a summit with the leaders of all 10 ASEAN nations that President Barack Obama will host next month in California.

China, which claims sovereignty of much of the territory in the South China Sea, rejects claims from countries like the Philippines and Vietnam and has bristled at U.S. warnings that its activities threaten the freedom of navigation in some of the world’s busiest commercial shipping lanes. Taiwan, Malaysia and Brunei also have overlapping claims in the strategically vital sea, through which around $5 trillion in world trade passes each year.

The U.S. says it takes no position on the claims but says developments in the South China Sea are a national security interest. It has urged that the disputes be settled peacefully and that a binding code of conduct be established for the area.

Tensions have been especially high since Beijing transformed seven disputed reefs into islands, where it is now constructing runways and facilities that rival claimants say can be used militarily. China has said it built the islands primarily to foster safe civilian sea travel and fishing.

In response, the U.S. sent a guided-missile destroyer close to one of the Chinese-built islands, called Subi Reef, in October in a challenge to Beijing’s territorial claims, sparking warnings from China. U.S. officials vowed to continue maneuvers to protect freedom of navigation and overflight.

Recent developments, including China’s movement of an oil rig into a zone disputed with Vietnam and warnings against Philippines overflight of what it claims to be its territory, have raised those levels of concern. China dismisses the warnings as unwarranted, but has harshly criticized a U.S.-Philippines defense pact that allows American forces, warships and planes to be based temporarily in local military camps. China says that will “escalate tensions and undermine peace and stability in the region,” echoing language the United States uses to criticize China’s actions.