Chinese Premier Li Keqiang will host South Korean President Moon Jae-in and Japanese Prime Minister Shinzo Abe for the meeting in Chengdu on Tuesday.
The visiting leaders will also hold separate talks with President Xi Jinping, Chinese vice foreign minister Luo Zhaohui told reporters at a briefing.
The meeting of regional powers comes as tensions have risen between Washington and Pyongyang after North Korea carried out a series of rocket launches.
Nuclear talks between the North and the United States have been largely stalled since the collapse of a February summit in Hanoi between President Donald Trump and North Korean leader Kim Jong Un.
Pyongyang has issued a year-end ultimatum, promising an ominous “Christmas gift” if Washington does not come up with some concessions.
China, an old ally of Pyongyang, introduced a draft joint UN resolution with Russia this week seeking to lift some of the punitive measures that have been enforced on North Korea over its nuclear activities.
Tuesday’s summit will aim to “have a constructive effect on achieving peace and stability on the Korean peninsula”, Luo said, adding however that the leaders would not be discussing the proposed UN resolution.
There are also tensions between Japan and South Korea, as their ties have deteriorated over Tokyo’s use of forced labour during World War II.
The diplomatic friction has resulted in tit-for-tat trade restrictions and the scrapping of a military information-sharing pact between the two.
Luo said China “did not feel that the disagreement between South Korea and Japan had any negative influence on trilateral cooperation”.
He added that the three leaders would discuss “accelerating” negotiations for a trilateral free trade deal.