Historians from China and Japan have given up cowriting a single history of Sino-Japanese relations in a joint study project sponsored by the two governments because of the apparent huge gaps in their views and time constraints, Japanese participants said Tuesday.

"We have never thought of (cowriting a single history) given the time frame. It's impossible," said University of Tokyo professor Shinichi Kitaoka, head of Japan's team.

Instead, the scholars agreed each side will separately write its own versions of bilateral history texts and exchange written comments if they disagree on controversial points, Kitaoka told reporters.

The project kicked off in December as part of government efforts to narrow perception gaps in history between Japan and China. The scholars -- 10 from China and 10 from Japan -- will try to finish their joint study by June 2008 and later compile and publish a series of essays on bilateral relations, Kitaoka said.

The historians also agreed on a list of major historical events that must be discussed in each chapter, including the 1937 Nanjing Massacre and a 21-point demand Japan made on China in 1915.

The "comfort women" issue was not included in the agreed list. But each writer can discuss the topic in their essay if they want to do so, Kitaoka added.

"Comfort women" is Japan's euphemism for women forced into sexual servitude at Japanese military brothels during the 1930s and 40s. Some Japanese lawmakers claim they were not "sex slaves" as publicly testified by many of the victims, drawing criticism from China, South Korea and elsewhere that claim such denials are an attempt to whitewash Japan's wartime misdeeds.