Japan on Tuesday ruled out any immediate plan to join the Beijing-backed Asian Infrastructure Investment Bank (AIIB), categorically denying a news report that its ambassador to China said Tokyo is likely to take part.

The Financial Times reported that Masato Kitera, Tokyo's envoy in Beijing, said in an interview Japan is likely to join the AIIB within a few months, a move that would leave Washington as the only big holdout.

But Chief Cabinet Secretary Yoshihide Suga said Tuesday the ambassador had not made any such comment and Japan's position on the AIIB had not changed.

"I have been informed that it is not true that Ambassador Kitera made such remarks forecasting (Japan's) participation," Suga told a news conference.

The report comes just before the end-March deadline China has set for participation in the bank as a founding member.

Australia, Britain, France, Germany, Italy and Russia have all said they intend to join the Beijing-headquartered $50 billion institution, despite scepticism in Washington and Tokyo. China's neighbour and long-time foe Taiwan said Monday it would also make a formal application to join.

"Japan is dubious about whether (the AIIB) would be properly governed or whether it would damage other creditors," Suga said. Japan is a key player in the Asian Development Bank (ADB), which would be a rival.

"Anyway, I think it's impossible for Japan to take part today," the government's top spokesman said, adding that Tokyo would work together with Washington, its top ally, and other countries to ask Beijing for clarification.

The new multinational lender is seen as a threat to the World Bank and the ADB, two institutions that are heavily influenced by the US and Japan.

Washington has been left increasingly isolated in its opposition to the AIIB, which opponents claim could end up as a Chinese vehicle that has low standards on governance, the environment and social issues.

President Barack Obama's administration has waged an intense but low-profile lobbying campaign against it, but has watched with frustration as allies around the world pile in, with some hoping to curry favour in Beijing and others not wanting to miss out on a lucrative part of the world.

China is expected to foot the bulk of the initial money needed to get the AIIB started, with donations from other members set to increase the size of the overall fund to more than $100 billion.