China and Japan are expected to release in Tokyo today a joint report that acknowledges Japan's invasion of China during the Second World War - a document that analysts said was a positive start to removing a long-standing irritant in bilateral ties.

The report, featuring 13 articles by Chinese historians and an equal number by their Japanese counterparts, is likely to cover historical and contemporary relations between the two nations, a source close to the compilers of the report told China Daily yesterday.

Historians on both sides are agreed on the fact that Japan invaded China, the source said, but due to wide differences, the report may not cover post-war history. "Research will continue on that part," the source said.

The report is also expected to touch upon events such as the 1937 Nanjing Massacre, during which, China says, Japanese invaders slaughtered 300,000 civilians in the city.

The report, which will record views from both sides in case of disagreements, is the result of discussions spread over three years among 30 historians from the China-Japan Joint History Research Committee.

In October 2006, President Hu Jintao and then Japanese Prime Minister Shinzo Abe agreed to set up the committee to salvage bilateral relations, which had touched bottom during the time of Abe's predecessor, Junichiro Koizumi.

Rows over the understanding of history, at times, soured bilateral relations between the Asian neighbors.

The most pronounced spats dealt with Japan's revision of its history textbooks and its leaders' visits to the Yasukuni Shrine, which houses the tablets of war criminals such as Hideki Tojo.

A Beijing-based analyst said the report was the latest sign of warming ties between Beijing and Tokyo.

"Both nations used to put history related issues on the back burner and focused on the economy and current affairs," Niu Zhongjun, a professor at China Foreign Affairs University, said yesterday.

The release of such a report showed that ties have been strengthened to a level where both nations could address "this sensitive and thorny matter", he said.

Calling the report a "milestone", Japanese writer and commentator Kato Yoshikazu said the document, for the first time, "offered an authoritative version of history and enabled both peoples to clear their doubts".

Yoshikazu, however, cautioned that the report could arouse opposition from Japan's right-wingers.

"Debates are welcome, but we shouldn't politicize the report," he said.

Niu also warned that different perceptions of history will prevail between China and Japan, and "they will not be solved overnight."

An official from the Japanese embassy in Beijing did not confirm the release of report.

"The two sides are working on the final arrangement of the meeting and release," he told China Daily yesterday, adding the joint research was conducive to "promoting mutual understanding and trust between Japan and China".

Sino-Japanese relations have improved since Japanese Prime Minister Yukio Hatoyama took over in September. "Hatoyama's pro-Asia policy is in favor of Beijing", Niu said.

Earlier this month, Hatoyama told visiting Chinese Vice-President Xi Jinping that Japan should courageously face up to history.