US Secretary of State John Kerry warned China on Friday against unilateral moves to set up a new air defence zone, saying such a step could threaten regional stability at a time of heightened tensions.

After a day of talks with senior Chinese leaders including President Xi Jinping, Premier Li Keqiang and Foreign Minister Wang Yi, Kerry stressed that he had also highlighted the need to ease concerns over Beijing's territorial ambitions.

The top US diplomat's trip comes at a pivotal moment for the region, with flaring disputes between Beijing and Tokyo over their World War II history and disputed islands in the East China Sea sending relations between the Asian powers plummeting to their lowest point in recent years.

The issue of North Korea was also high on the agenda, with both sides putting specific ideas on the table for how to prod Beijing's belligerent ally to take concrete steps towards denuclearisation.

Washington was deeply angered when Beijing last year declared an air defence identification zone (ADIZ) over the East China Sea which includes the disputed islands, saying it could lead to confusion high in the skies.

Kerry told reporters he had warned Beijing against any further such moves, amid reports that China is considering a similar ADIZ over the South China Sea, where it has competing claims with several countries including the Philippines -- another US security ally.

"We've made it very clear that a unilateral, unannounced, unprocessed initiative like that can be very challenging to certain people in the region, and therefore to regional stability," Kerry stressed.

Any future such moves should be done "in an open, transparent, accountable way," he said, adding China should meet "the highest standards" of openness "to reduce any possibilities of misinterpretation".

His talks had also focused on "the specific road ahead" to resolve the competing maritime claims which have poisoned relations, and while China agreed it should be done peacefully, Kerry referenced Beijing's belief that it has a "strong claim based on history, based on fact".

For his part Wang "introduced the history of the East China Sea and South China Sea issues and elaborated on China's firm stance", Beijing's foreign ministry said in a press release.

- Zone not a claim of sovereignty -

He stressed that "no one can shake our determination to safeguard national sovereignty and territorial integrity", it added.

Beijing requires aircraft flying through its ADIZ to identify themselves and maintain communication with Chinese authorities, but the zone is not a claim of sovereignty.

Nonetheless fears of an aerial or maritime clash over the East China Sea islands have spiked following its declaration by Beijing. Chinese and Japanese patrol boats regularly shadow each other in the waters near the islands.

At the same time Beijing has been acting increasingly assertively in the South China Sea, which it claims almost in its entirety.

Kerry, who arrived in Beijing from Seoul on the second leg of an Asia tour, reiterated Friday that North Korea must take "meaningful, concrete and irreversible steps towards denuclearisation".

And he said the Chinese leaders had been "forceful" in reaffirming their commitment to that goal.

Wang said that China will never allow any chaos or war on the Korean peninsula, according to the official news agency Xinhua, quoting him saying: "China is serious on this. We not only say so, but do so."

Chinese state media, however, remained focused on the historical issues at play, with the China Daily newspaper on Friday running an editorial cartoon depicting Japanese Prime Minister Shinzo Abe offering a Valentine's Day rose to a dead kamikaze pilot's skull.

The cartoon appeared to be a reference to a recent bid by the Japanese city of Minami-Kyushu for World War II kamikaze fighters' farewell letters to be included in a UNESCO world heritage register, a move that drew swift condemnation from Beijing and Seoul.

The Global Times newspaper, which is close to China's ruling Communist Party, wrote in an editorial Friday that while Kerry's visit to Beijing is expected to be a "smooth" one, the US' promised "pivot" to Asia "has triggered pressure on China's strategies".