Kim expressed 'concern' over US, N. Korea 'impasse' to Xi: KCNA

North Korean leader Kim Jong Un expressed "concern" about the deadlock in denuclearisation discussions in his talks with Chinese President Xi Jinping, Pyongyang's state media reported Thursday.

Kim "raised concern about the impasse created in the process of improving US-DPRK ties and in denuclearisation talks", the official KCNA news agency said.

Kim said Pyongyang's "basic position of pursuing a peaceful resolution through dialogue remains unchanged", it added.

China is the North's main diplomatic backer and key trade partner, whose forces were instrumental in fighting for it during the 1950-53 Korean War.

According to KCNA, Beijing issued a ringing endorsement of the North's position.

"Xi Jinping said that the legitimate issues raised by the DPRK are rightful demands and that he fully agrees that the DPRK's reasonable interests should be justly resolved," it said.

It added that Xi accepted an invitation by Kim to visit the North "at a convenient time" and "informed him of related plans".

It would be Xi's first trip to Pyongyang since he took power in 2012.

But it is not the first time Pyongyang has said Xi has accepted such an invitation -- it did so in March last year after Kim went to Beijing for the first time as leader, but Xi has yet to make a return journey.