The U.N. Security Council will hold an informal poll Thursday on the dozen candidates competing to succeed Ban Ki-moon as secretary-general on Jan. 1.

The 15 council members have decided to keep the vote secret — a sharp contrast to the informal polls 10 years ago which were made public and led to Ban's election to the world's top diplomatic post.

Japan's U.N. Ambassador Koro Bessho, who holds the rotating council presidency, reiterated he would only be confirming that the poll was held behind closed doors.

According to the U.N. Charter, the secretary-general is chosen by the 193-member General Assembly on the recommendation of the Security Council. This generally means the council's five permanent members — the U.S., Russia, China, Britain and France — have veto power over the candidates.