Chinese President Xi Jinping has told Kim Jong-un that Beijing supports a second summit between the North Korean leader and US President Donald Trump, adding that he hopes they "meet each other halfway", according to state media.

The report by Xinhua news agency on Thursday came a day after Kim concluded an unannounced two-day trip to China, North Korea's major diplomatic ally and primary source of aid and trade.

"Political settlement of the (Korean) Peninsula issue faces a rare historic opportunity," Xi said during Kim's visit to the Chinese capital, according to Xinhua.

For his part, Kim said North Korea will make efforts to "achieve results that will be welcomed by the international community" at the next summit with the United States, China's official news agency added.

Kim said he hoped relevant sides would take North Korea's "reasonable concerns" seriously and actively respond to them to promote a comprehensive resolution to the Korean Peninsula issue.

In a report also on Thursday, North Korea's state media KCNA said that Kim and Xi had in-depth discussions on how to "jointly study and steer" the situation on the Korean Peninsula and denuclearisation talks.

The trip to China came a week after Kim, in his annual New Year's address to the nation, renewed his commitment to denuclearisation but warned that Pyongyang may change its approach to nuclear talks if Washington persists with sanctions.

At a landmark summit in Singapore last year, Kim and Trump signed a vaguely-worded pledge on denuclearisation. But progress has since stalled with Pyongyang and Washington - which stations 28,500 troops in South Korea - disagreeing over what that means.

The US insists that United Nations sanctions must remain in place until North Korea gives up its weapons, while Pyongyang wants them eased immediately.

China also wants the sanctions relaxed and Xi said he "hopes that the DPRK and the United States will meet each other halfway" according to Xinhua, using the initials of North Korea's official name.

Xi "spoke highly of the positive measures taken by the DPRK side", it added.

'Imminent' summit?

North Korea has carried out six nuclear blasts and launched missiles capable of reaching the whole of the US, but has carried out no such tests for more than a year, and blew up the entrances to a nuclear testing ground it said it no longer needed.

Pyongyang has rejected demands for what it calls its "unilateral" disarmament as "gangster-like".

Each of the previous Kim-Xi meetings have come shortly before or after the North Korean's summits with either Trump or South Korean President Moon Jae-in.

Trump said on Sunday that the US and North Korea are negotiating the location for their next summit, a meeting South Korean President Moon Jae-in said on Thursday was "imminent".

Kim's visit to China coincided with negotiations between US and Chinese officials in Beijing to resolve a bruising trade dispute between the world's two largest economies that has roiled financial markets.