Japan, China and South Korea have agreed in principle to hold a trilateral summit in early May, possibly from May 8 to 9, several diplomatic sources said Tuesday.

The three-way summit was last held in November 2015 in Seoul. At the meeting to be chaired by Japan, Prime Minister Shinzo Abe, Chinese Premier Li Keqiang and South Korean President Moon Jae-in are expected to discuss steps to boost cooperation in the fields covering the economy, environment and culture.

To lay the groundwork for the trilateral summit, the Japanese and Chinese governments are planning for Chinese Foreign Minister Wang Yi to visit Japan in April, other diplomatic sources said. Wang was promoted to state councilor in charge of foreign affairs on Monday.

At a news conference in Beijing, Li said he is planning to visit Japan in the first half of this year for the trilateral summit.

Li will be the first Chinese premier to visit Japan since Wen Jiabao's trip in May 2011, while Moon will be the first South Korean president to come to the country since Lee Myung-bak's visit in December that year. Japan's relations with its two neighbors have been strained in recent years due to differences over history and territory.

In bilateral summits, Abe is expected to discuss with Li his plan to visit China and with Moon the issue of "comfort women," a euphemism for the women and girls who were procured for Japan's wartime military brothels, many of whom were from the Korean Peninsula.