Trump on Sunday stepped into North Korean territory in the Demilitarized Zone, the first time a sitting US president has ever set foot in the former enemy country.

Moments after the historic gesture, Trump brought Kim back over the dividing line separating North and South Korea for a meeting where they agreed to start working-level talks on Pyongyang's nuclear weapons.

"These developments should be welcomed," Chinese Foreign ministry spokesman Geng Shuang said at a regular press briefing.

"In particular, the DPRK (North Korea) and the United States agreed to resume working level consultations soon, which is of great significance. China supports this," Geng said.

The historic DMZ meeting came around a week after Xi Jinping visited Pyongyang -- the first trip there by a Chinese president in 14 years as the two Cold War era allies further mended ties that cooled over North Korea's nuclear activities and Beijing's subsequent support for UN sanctions against its neighbour.

Geng said Xi's recent visit to Pyongyang had "injected new impetus" into the nuclear talks.

He urged both sides to "seize the opportunity, move in the same direction and actively explore effective solutions to each other's concerns" to ensure progress in efforts to denuclearise the peninsula.

Analysts had said Xi might use his visit to North Korea as leverage when he met Trump for talks on their trade spat at the G20 in Japan at the weekend.

Xi and Trump agreed on Saturday to a ceasefire in the trade war, with the US leader vowing to hold off on further tariffs on Chinese imports as negotiations continue.