TOKYO/MOSCOW - The China-led $50 billion Asian Infrastructure Investment Bank (AIIB) continued to get more members, with the latest being Taiwan and Norway saying they would join the institution, while Japan is mulling the idea and Russia has said it will become a founding member on April 14.

At least 44 countries have applied for membership in the AIIB with the rights of founding countries.

The initial applications are to be processed on March 31.

Russia's First Deputy Prime Minister Igor Shuvalov has said that Russia has applied to participate in the AIIB as a founding member.

Finance Minister Taro Aso reiterated Japan's concerns about governance at the AIIB, its debt sustainability and environmental and social safeguards.

"Unless these conditions are secured, Japan has no choice but to be very cautious about joining," Aso told reporters after a cabinet meeting.

At the same time Aso didn't rule out the possibility of the country's future participation in AIIB, saying that Japan plans to "watch the bank's development."

The AIIB is considered a potential rival to the US-based World Bank. Earlier in March US Treasury Secretary Jack Lew warned that US-based international financial institutions risk losing "international credibility and influence."

The new development bank, which was announced just five months ago, is becoming a massive headache for the US, which has in vain been trying to convince allies to stop joining the AIIB.

Like the World Bank, the bank would provide loans to developing countries in Asia for infrastructure projects. But unlike the World Bank, China will hold the reins of the AIIB.

The US has voiced concern that the institution won't meet high governance standards, but in reality it appears opposed to the bank as it signals a growing Chinese influence in the region, and in global politics.

Norway said on Tuesday that it intends to join the Asian Infrastructure Investment Bank as a prospective founding member to promote closer ties to the Asia-Pacific region.

Norwegian Foreign Minister Boerge Brende said his country is a major contributor to global development efforts and wants to be among the countries in "further refining the structure and mission" of the Chinese-led bank.

"We hope the launch of the (bank) will help address a widely acknowledged infrastructure funding gap in Asia," Brende said. "China's initiative highlights the increasing weight of the new and emerging powers."

Taiwan presidential office spokesman Charles Chen said joining the AIIB would help Taiwan in its efforts at regional economic integration and raise the possibility of joining other multinational bodies.

Asked about Taiwan's application, Chinese foreign ministry spokeswoman Hua Chunying said: "Our principle has not changed, and that is it will be an open, inclusive and multilateral organization which we welcome all sides to join.

"But for Taiwan's application to join, it should abide by the relevant principles, which is to avoid the problem appearing of 'two Chinas' or 'one China, one Taiwan'."

Applications to join the AIIB were submitted by South Korea and a number of leading European economies, including the UK, France, Germany, Italy, Switzerland and Luxembourg.

Kyrgyzstan too has applied to join AIIB. The country is expected to become a bank member on April 9.

Sweden will also apply to join the bank, the country's finance minister said Monday, becoming the latest European country to join the institution despite concerns of the US.