Japan is about to step up its campaign to win a permanent seat on the United Nations Security Council.

Japanese Prime Minister Junichiro Koizumi on Tuesday said he will push for expansion of the Security Council when he addresses the United Nations General Assembly next month.

Mr. Koizumi told reporters that Japan, as the world's second largest economy and second biggest contributor to the United Nations, should join the United States, Britain, France, China and Russia at the elite table.

Japanese media reports say the prime minister will ask the world body to expand the number of permanent Security Council seats from five to up to 10. Until now, Japan, Germany and other nations defeated in WWII have been excluded from permanent seats.

Prime Minister Koizumi acknowledges expanding the Security Council, whose members have automatic veto power, is a difficult issue.

Years ago, as a young Cabinet minister, Mr. Koizumi opposed pursuing a permanent seat, expressing concern about requirements for Japanese forces to join U.N. peace-keeping forces in a combat role.

Some analysts say Japan would have to change its pacifist constitution to win wider support among other nations.

Teikyo University Security Professor Toshiyuki Shikata is a former chief commander of Japan's Self Defense Forces. He predicts two permanent members will be the most difficult for Japan to win over.

"It is very doubtful for China and Russia," he said. "They will speak something. It's too early or Japan should amend the constitution, something like that."

Earlier this month, U.S. Secretary of State Colin Powell said Japan should revise its constitution if it desires a permanent seat.

But on Tuesday, a Japanese cabinet spokesman said the United States supports Tokyo's bid for a permanent Security Council seat and has said that is not contingent on Japan amending its constitution.

Japan has been a full member of the U.N. since 1956 and has served seven times as one of the Security Council's rotating members. It launched its first official bid for a permanent seat in 1994.