Japan's junior coalition party, Komeito, says it will postpone its leader Yamaguchi Natsuo's three-day visit to China, which was scheduled from Monday.

The party said on Saturday that China told it the timing was not appropriate given the state of bilateral relations, indicating that Japan's release of treated and diluted water from the crippled Fukushima Daiichi nuclear power plant into the ocean is behind it.

Komeito says it consulted with China to reach the decision to postpone the visit.

Yamaguchi had said he wanted to visit China for the first time in four years to meet members of the Chinese Communist Party's leadership and hand Prime Minister Kishida Fumio's letter to Chinese President Xi Jinping.

Komeito quoted the Chinese side as saying it attaches importance to the exchanges the party has maintained for a long time, and recognizes the effort it made to make Yamaguchi's visit happen.

China strongly opposes Japan's release of treated and diluted water from the Fukushima Daiichi power plant into the ocean, and has suspended all imports of seafood from Japan.