If the United Nations is to be seen as a truly credible institution, it is necessary to change the structure of the outdated Security Council, Japan's ambassador to the United Nations said Tuesday.

"The reform of the Security Council is long overdue," said Koro Bessho.

Together with Brazil, India and Germany, Japan is one of the countries collectively known as the Group of Four that aspire to become permanent seat holders on a restructured council that they hope to realize.