The offer of being a founding member of the Asian Infrastructure Investment Bank (AIIB) is still open but the ball is in Japan's court, said Chinese Finance Minister Lou Jiwei Friday.

The chance to be an AIIB founding member is available for all Asian countries including Japan by March 31, Lou said at a press conference on the sidelines of the ongoing national legislative session.

Japanese government has been updated with the result of talks among the bank's current founding members, Lou said.

"They told us they are considering. Whether Japan will join, we do not know. It is Japan's own decision," he said.

Lou confirmed that some European countries, including major ones, have expressed the intention to join.

But current founding members agree that AIIB will consider Asian countries first and the membership of countries outside the region will be the next step, he said.

Currently 27 countries have confirmed to join AIIB, an initiative proposed by China in a bid to finance infrastructure projects across Asia.

Vice Finance Minister Zhu Guangyao told media Tuesday that the bank will be set up within 2015.

"It is hard to predict how many countries will join in the future. It is not up to China but all founding members," Lou said.