(Yicai Global) Dec. 19 -- The Asian Infrastructure Investment Bank said today that its board of governors had given the Cook Islands, Vanuatu, Belarus and Ecuador the okay to join the bank, bringing AIIB's total approved membership to 84.

The four prospective members will officially join AIIB once they complete the required domestic processes and deposit the first installment of capital with the bank. The shares allocated to the new prospective members come from AIIB's existing pool of unallocated shares.

Established in 2015, the AIIB opened for business in January last year with 57 founding members. It has expanded in four rounds of additions. The US and Japan have not yet joined.

The bank approved a USD250 million loan to construct a natural gas supply network in Beijing on Dec. 11. It has given the green light to over USD3.7 billion of backing for more than 20 projects.