U.N. Secretary-General Kofi Annan says urgent action is needed to preserve the Nuclear Nonproliferation Treaty. He spoke Monday to representatives from nearly 190 countries at the start of a month-long conference on the treaty. Mr. Annan says the treaty is under great stress. He also suggested that North Korea's recent withdrawal from the treaty threatens the agreement's credibility. Mr. Annan and other delegates also called on nuclear powers to make more effort to cut their weapons arsenals. U.S. Assistant Secretary of State Stephen Rademaker rejected the criticism, referring to arms control agreements that will reduce the number of U.S. warheads. Mr. Rademaker also made clear that the United States wants the conference to focus on North Korea and Iran, which the United States accuses of trying to develop a nuclear weapon.