Japanese Prime Minister Fumio Kishida is considering attending a summit of leaders from the North Atlantic Treaty Organization (NATO) in late June to spur coordination with the West over Russia's invasion of Ukraine, sources familiar with the matter said.
The move would mark an unusually aggressive stance for a Japanese leader although Kishida has repeatedly condemned Russia over what he has described as a "war crime" against Ukraine.
Moscow has called its action a special operation.
In the past, Japanese leaders have maintained a careful line on their relations with Russia as the two countries have wrangled over decades-old territorial disputes.
A government spokesman said officials would be unable to comment on the matter, which was first reported by Kyodo news on Saturday.
The NATO summit takes place on June 29-30 in the Spanish capital Madrid, which would likely overlap with the campaign ahead of elections in Japan penciled in for July 10.
Kishida will make a final decision later, taking into account the political situation before the upper house elections, Kyodo reported, citing government sources.
NATO has invited Japan to the summit, along with Australia, New Zealand and South Korea as its partners in the Asia-Pacific region.
Kishida plans to arrive in Madrid after attending a meeting of the Group of Seven (G7) industrialized nations in Germany, the sources, who asked not to be named, told Reuters.
Kishida's presence at the summit would be welcomed as delivering a strong message of international solidarity on the Ukraine crisis, Kyodo's sources were quoted as saying.