It is not surprising that the 18-month-old Asian Infrastructure Investment Bank (AIIB) obtained the highest level of credit rating from Moody's Investors Service, an international trade expert said.

"This is no easy achievement especially given the short history since the establishment of this international institution," Anthony Mak, director of Hong Kong Trade Development Council's New York office, said in an interview with Xinhua on Friday.

"But given its strong balance sheet, with subscribed capital already larger than many other multinational development banks with much longer history, it is also not surprising to me that the AIIB wins such laurels," said Mak.

On Thursday, Moody's assigned the AIIB a long-term foreign currency issuer rating of Aaa and a short-term foreign currency issuer rating of Prime-1 with a stable outlook.

The credit rating agency attributed such high ratings to the strength of the bank's governance frameworks, including its policies on risk management, robust capital adequacy and strong liquidity position.

Mak believed that the AIIB has a "world-class" governance structure. He explained that the AIIB has "an independent Internal Audit Office and an Ethics Office directly reporting to its president. The president reports to an independent Board of Directors, supplemented by the work of a Compliance, Effectiveness and Integrity Unit."

The Beijing-based AIIB was officially established in December 2015 and It opened its doors for business in January 2016. It is a multilateral development bank initiated by China and supported by 80 member countries and regions to finance infrastructure improvement in Asia and serves as a key financing mechanism for the China-proposed Belt and Road Initiative.

To date, the bank has approved $2.49 billion in financing for 16 infrastructure projects in nine countries. Twelve of the projects were co-financed, while four were standalone projects prepared by AIIB staff.

Mak believed that a strong credit rating by Moody's for the AIIB can further enhance the bank's financing capacities in the future.

"A strong credit rating for the AIIB, and therefore reduced cost of debt financing, is critically important for the successful implementation of the multinational Belt & Road Initiative," he said.