Diplomats expressed frustration Tuesday during a U.N. General Assembly session about long-overdue negotiations to reform the Security Council.

Japan's Ambassador to the United Nations, Koro Bessho, was among those who highlighted the lack of tangible progress so far.

"If we fail to make significant headway in this coming session, I fear that the legitimacy and viability of the IGN process itself will come into question," he said, referring to the intergovernmental negotiations on the reform of the powerful 15-member council.