Following Britain, major US allies such as France, Germany and Italy have agreed to join the China-backed Asian Infrastructure Investment Bank (AIIB), the Financial Times reported, citing European officials.
In addition, Australia, a key US ally in the Asia Pacific region, is set to decide on joining the international bank next week. China's state-owned Xinhua news agency said South Korea, Switzerland and Luxembourg were also considering joining the AIIB.
The moves from the countries come as a severe blow to the Obama administration that was working hard to keep them out of the institution.
Britain has earlier announced its intention to become a founding member of the AIIB – a Chinese-led initiative that is expected to rival the World Bank and the Asian Development Bank in the Asian region.
The move has angered Washington, which said it is wary of Britain's "constant accommodation" of China.
In October 2014, representatives of 21 Asian nations convened in Beijing to inaugurate the AIIB, which is focused on providing funding to infrastructure projects within Asia. The bank was initially capitalised with $50bn (£31bn, €39.5bn), half of which was funded by China.
Britain is the first major Western country to apply to become an AIIB member. It will meet other founding members in March to discuss governance and accountability arrangements.
George Osborne sees opportunities
"Joining the AIIB at the founding stage will create an unrivalled opportunity for the UK and Asia to invest and grow together," said Chancellor George Osborne.
"We are wary about a trend toward constant accommodation of China, which is not the best way to engage a rising power," a US official earlier told the Financial Times, expressing concern.
Subsequently, Australia indicated its desire to join the bank, with Prime Minister Tony Abbot saying Canberra was "looking very carefully at this and we'll make a decision in the next week or so".
Responding to the media reports, Washington's top diplomat for East Asia said the US concerns about the AIIB remained, but it was up to individual nations to decide on whether to join the bank.
"Every government can make its own decision about whether the way to achieve that goal is by joining before the articles of agreement are clarified or by waiting to see what the evidence looks like as the bank starts to operate," US Assistant Secretary of State for East Asian and Pacific Affairs Daniel Russel said in Seoul.