Japan, China and South Korea are currently arranging to hold their annual three-way summit in December, diplomatic sources said Sunday.

But relations between Japan and South Korea have worsened recently due to historical and trade issues, and the scheduling of the trilateral summit may be adjusted depending on the course of the dispute.

China, which this year holds the rotating chair for the trilateral framework, had hoped to organize the leaders' meeting much earlier, following the summit of Group of 20 leading economies in Osaka in late June, the sources said.

But Japan told China that Prime Minister Shinzo Abe's schedule would be tight because of other political events, including a summit of the Group of Seven major industrialized nations in France in late August, according to the sources.

China is now proposing that the trilateral summit be held in December and South Korea has already agreed to adjust President Moon Jae-in's schedule to that end, they said.

The foreign ministers of the three Asian countries may meet on the outskirts of Beijing on Aug. 21 to coordinate the schedule for the summit, set to be chaired by Chinese Premier Li Keqiang, as well as the major agenda items.

The three countries last held their summit in May 2018 in Tokyo.

For Abe, the summit will serve as a good opportunity for him to create a more favorable environment for a planned state visit to Japan next spring by Chinese President Xi Jinping.

It is almost certain that Abe will hold separate talks with Li on the sidelines of the summit to discuss Xi's trip.

But whether Abe and Moon will meet remains uncertain at this point, even if the summit takes place as planned.