In yet another effort to promote Japan's quest for a permanent seat on the United Nations Security Council, Prime Minister Yoshiro Mori will write most of the U.N. member nations as early as next week to reiterate calls for UNSC reforms, government sources said.

In letters to be sent to 165 of the 189 U.N. member countries, Mori will specifically stress how important Japan feels it is to increase the number of both permanent and nonpermanent council members, the sources said Monday.

This is the second installment of Mori's letter-writing campaign. In August, he sent letters saying the same thing to the same 165 nations ahead of the U.N. Millennium Summit, which was held in New York. The summit was attended by kings, presidents and prime ministers from most of the U.N.'s 189 member countries. Some U.N. member nations, however, oppose increasing the number of permanent UNSC members. The Security Council is composed of five permanent members and 10 rotating nonpermanent members. The permanent members -- the United States, Russia, Britain, France and China -- each have the power of veto.