"With the one trillion a year extra that's needed, even if all the banks that have been proposed come online, we still won't be able to meet the need. So, we welcome all these efforts to increase infrastructure financing and look forward to working closely with any of the new institutions," he said, adding "there is more than enough business for everybody."

World Bank pares 2014 outlook

Asia banking on expansion

In terms of advice for the AIIB, Kim said the only advice that he would give is that the AIIB should see the World Bank as very willing and open partners.

"We would say, please, take advantage of our 70 years of experience in doing this kind of business, and let's see how we can work even more closely together," he said.

With a preliminary capital scale of $50 billion, the AIIB is expected to be funded by its members in installments and may grow following future business expansion.

The final capital sizes and shares of various parties shall be settled by the AIIB founding members through consultation and negotiations, Lou Jiwei told Xinhua in early March. "If conditions become ripe, it may also expand its business beyond the region," he said.

In April, Chinese Premier Li Keqiang said at the 2014 Boao Forum for Asia that China is ready to intensify consultations with relevant parties in and outside Asia on the preparations for the AIIB and hopes that the bank can be officially launched at an early date.