SYDNEY, April 15  -- A leading Australian expert on Chinese affairs said Japanand the United Stateswere now on the outer after declining to join the China-proposed Asian Infrastructure Investment Bank (AIIB) as founding members.

Founding membership will be finalized on Wednesday, but both nations have decided not to take part in the historic establishment of the Chinese-led bank which now has 50 prospective founding members, including economic powerhouses Germany, South Korea, Britain and France.

Instead of being part of the foundation stage, when the AIIB's ultimate structure and regulations will be established and where they could have been involved, Professor James Laurenceson of the University of Technology Sydney said the United States and Japan had lost their chance.

"The ball is now in the U.S. and Japan's court," Laurenceson, deputy director of the Australia China Relations Institute, told Xinhua. "The rest of the world has been pretty clear they're keen to draw China into the international fold. It's really just the U. S. and Japan that are sitting on the outside."

"Personally I think it would have been good for the U.S. and Japan to have joined. All their concerns would be far better managed if they were actually founding members of this bank," he added.

The major European nations and Australia resisted strong pressure from Washington by signing onto the AIIB.

"The big story of the last month or two is the broad support that the AIIB has attracted -- that's really what has changed," Laurenceson said.

"A group of countries like-minded with Australia have joined the bank. A broad coalition of nations is supporting China to take a more active role in economic management in one of the most important regions in the world."

The AIIB, once established, will provide financing for roads, railways, airports and other infrastructure projects in Asia.

Australia applied to join on March 29, two days before the cut- off date to be a founding member involved in the establishment process.

The Australian government last week announced that the former boss of the prime minister's department, Ian Watts, would head a team to negotiate Australia's position on the proposed AIIB.

Laurenceson said the United States and Japan were reluctant to change the current global financial balance of power held by the International Monetary Fund (IMF) and World Bank (WB), which they largely control.

Both countries have also expressed fears China would dominate the AIIB voting, but Laurenceson said the fact so many countries were now on board meant China's control was already diluted -- which he said is what China always wanted.

"The proposed AIIB is now clearly a more multilateral one," he told Xinhua. "China's intention in the beginning was for it to be a more multilateral institution."

"But it's still a challenge (to the United States and Japan). But the rest of the world doesn't see this as a problem."

The AIIB seeks to complement the roles of the IMF and WB. Voting rights for members in the AIIB will be based on their current GDPs.

As for corporate governance, Laurenceson said China had impressed upon the founding members that this was vital to the success of the new bank.

"I see China adopting very high standards and encouraging this bank to adopt very high standards, because if it doesn't it is going to reflect badly on its chief sponsor, which is China," he said.

"So China has every reason to make sure this bank maintains high standards in its lending processes and decisions on where to invest."