TOKYO—China requested Japan not make the South China Sea the focus of upcoming talks between Prime Minister Shinzo Abe and Chinese leaders, sources close to bilateral relations said Thursday.

Over the next few days, Abe is expected to meet with Chinese President Xi Jinping on the sidelines of the Asia-Pacific Economic Cooperation forum leaders' summit in Vietnam, and then he will likely hold talks with Chinese Premier Li Keqiang while both attend Association of Southeast Asian Nations meetings in the Philippines.

According to the sources, the Chinese government has urged Japan through diplomatic channels for the past several months not to emphasize maritime issues to the detriment of bilateral relations, often strained by territorial and historical grievances.

Beijing said that since Japan is outside the immediate area of the South China Sea, it should not "make noise" about the "sensitive issue," and should instead await the formation of a code of conduct between China and ASEAN, the sources said.

Despite Japan being some distance from the South China Sea, where China has overlapping territorial claims with some ASEAN members, it relies on key shipping channels in the area. Beijing has made a separate claim to the Japan-controlled Senkaku Islands in the East China Sea.

At the summits, Abe is likely to take note of China's claims while emphasizing Japan's position on maritime security: that the rule of law and freedom of navigation should prevail at sea, and that territorial disputes should be resolved peacefully in line with international law.

Leaving his office before his departure for Vietnam on Thursday afternoon, Abe told reporters he wants to hold "fruitful" meetings with Xi and Li.

"Through our strategic, mutually beneficial relationship, I want to...develop ties in every field," he said.

The meetings also offer a chance to seek further cooperation in tackling the nuclear and ballistic missile threat from North Korea, whose primary economic and diplomatic backer is China.

The Japanese government has said it is trying to arrange a trilateral summit in Tokyo with Li and South Korean President Moon Jae In before the end of this year, but no date has been fixed.

Next year will mark the 40th anniversary of the signing of a peace and friendship treaty between Japan and China.