United States Secretary of State John Kerry has appealed for China's help in bringing a belligerent North Korea back to nuclear disarmament talks.

The US foreign minister faced an uncertain response as the request on Friday was accompanied by demands for Beijing to roll back a series of increasingly aggressive steps it has taken to assert itself in territorial disputes with its smaller neighbours, the Associated Press news agency reported.

The United States will not accept North Korea as a nuclear-armed state. We will not accept talks for the sake of talks. US Secretary of State John Kerry

Kerry began his 24-hour visit by meeting Chinese President Xi Jinping and was later due to see other senior officials as he sought to underscore the Obama administration's commitment to refocusing US foreign policy on the Asia-Pacific amid a myriad of other global priorities, including climate change and Syria.

Yet, he faces a decidedly tough sell on both of his main agenda items: North Korea and regional tensions that have flared, particularly with Japan over conflicting maritime claims.

The extent of China's influence, and willingness to use it, with North Korea is unclear following a purge in the isolated country's leadership.

And China has angrily dismissed US criticism over its moves in the East and South China seas that have alarmed US allies like Japan and the Philippines.

In a stridently anti-Japanese editorial appearing on Friday, China's official Xinhua News Agency said the US must pressure Tokyo into ceasing its "provocative moves" or risk a regional conflict in the future.

In Seoul, South Korea, on Thursday, Kerry said the Obama administration wants to put new emphasis on getting North Korea back to stalled six-nation talks aimed at getting Pyongyang to give up nuclear weapons.

Leverage tested

"Let me be clear," he told reporters. "The United States will not accept North Korea as a nuclear-armed state. We will not accept talks for the sake of talks."

"No country has a greater potential to influence North Korea's behaviour than China, given their extensive trading relationship with the North," Kerry added.

But China's leverage with the North is being tested.

Diplomats say Beijing received no prior warning ahead of the December arrest and execution of North Korean leader Kim Jong Un's uncle, Jang Song Thaek, who had been considered Pyongyang's point man on China affairs and was a strong promoter of free trade zones being set up along their mutual border.

That came on the heels of Pyongyang's snubbing of Beijing's wishes when it conducted a missile test in late 2012, followed by the underground detonation of a nuclear device last spring.