Japan said Monday it will not sign a U.N. treaty that bans nuclear weapons and does not welcome its entry into force next year, rejecting the wishes of atomic bomb survivors in Japan who are urging the government to join and work for a nuclear-free world. The United Nations confirmed Saturday that 50 countries have ratified the Treaty on the Prohibition of Nuclear Weapons, paving the way for its entry into force in 90 days. The announcement was hailed by anti-nuclear activists, but the treaty has been strongly opposed by the United States and other major nuclear powers.