Tokyo: The Japanese government announced on Tuesday that it won't join the China-led Asian Infrastructure Investment Bank (AIIB).
It cited concerns regarding transparency in the new bank's operations, Efe news agency reported.
"Unless these conditions are secured, Japan has no choice but to be very cautious about joining," said Finance Minister Taro Aso.
March 31 was the deadline China set for countries to apply for founding membership of the AIIB it proposed in October 2014.
Japan has been reluctant to join a bank with the potential to weaken the power wielded by the US and Japan through the World Bank and the Asian Development Bank.
Aso also highlighted the importance of proper social and environmental impact assessment for potential AIIB-funded projects.
More than 40 countries have already signed up to the AIIB including Britain, Germany, Italy and France.
The bank, with an initial capital of $50 billion, will finance infrastructure projects in emerging and developing countries after it is officially launched later this year.