TOKYO - Japanese Prime Minister Fumio Kishida is leaning toward 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, Kyodo News reported, citing unnamed government sources.

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 Kyodo report before Monday.

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 pencilled in for July 10.

Kishida will make a final decision later, taking into account the political situation before the upper house elections, the government sources were quoted as telling Kyodo.

NATO has invited Japan to the summit, along with Australia, New Zealand and South Korea as its partners in the Asia-Pacific region.

Kishida's presence at the summit would be welcomed as delivering a strong message of international solidarity on the Ukraine crisis, the sources were quoted as saying by Kyodo.

(Reporting by Tetsushi Kajimoto; Editing by Raju Gopalakrishnan)