At a landmark June summit in Singapore, Mr Kim and Mr Trump pledged to work towards denuclearisation, but the pact was light on details and talks since have made little headway.
China is North Korea’s most important economic and diplomatic backer, despite anger over its neighbour’s nuclear and missile programmes. Ties have warmed in the last year as Pyongyang’s relations with both Seoul and Washington have also improved.
China also played a role in Trump’s meeting with Mr Kim, lending the North Korean leader an airliner for his trip to Singapore.
Diplomatic sources say Mr Xi will probably go to North Korea at some point soon, which would make him the first Chinese leader to do so since 2005.