The earliest issuance window will be "toward the end of the first half of 2018," to allow time for certain procedures, including the board of governors' approval of AIIB's 2017 financial statements as well as borrowing and swap documentation, Xinhua said citing a statement from Elbech.

Elbech said the minimum size of the bond would be $1 billion, but as demand for the first bond issue from AIIB may be strong, "we anticipate having to issue a larger size."

In terms of bond's maturity, Elbech said the choice would be between three and five years depending on investor demand at the time, Xinhua said.

He said the bank planned to cap its total borrowing volume at $3 billion in 2018.

In November, AIIB Vice President Thierry de Longuemar told Reuters the inaugural U.S. dollar bond would likely be launched in Europe sometime in 2018.

The AIIB, which has 80 member countries, was set up by China as its answer to the World Bank to help meet the estimated $26 trillion need for infrastructure spending in Asia through 2030.

(Reporting by Josephine Mason. Editing by Jane Merriman)