In a significant diplomatic setback for Japan, top leaders of the Group of Eight major countries are unlikely to refer to the need for reform of the United Nations Security Council in a joint declaration to be issued at their upcoming summit in Okinawa.

Government sources said Tuesday that the G8 leaders' declaration will probably emphasize the importance of strengthening the overall U.N. functions to address conflicts and other challenges facing the world, without making any specific reference to the U.N. Security Council.

The sources said that although Japan has insisted on including membership expansion and other reforms of the powerful Security Council in the declaration to promote its bid for a permanent seat on the 15-nation council, some G8 members, including Italy, are either opposed or reluctant to do so.