Japan goes off script at summit to slam North Korea SEOUL (Reuters) - Japan steered off the agenda at a nuclear security summit on Tuesday to hit out at North Korea's plans for a rocket launch next month, as U.S. President Barack Obama cautioned against complacency in dealing with the threat of nuclear terrorism. North Korea and Iran's nuclear weapons programs are not on the agenda at the summit in the South Korean capital, Seoul, and neither country was invited to the forum involving some 50 world leaders tasked with improving security at nuclear facilities. The secretive North has been widely criticized on the sidelines of the meeting, including by main ally China, but host Seoul has explicitly stated Pyongyang's weapons of mass destruction programs were off the table during the summit itself. Japanese Prime Minister Yoshihiko Noda used his opening speech at the summit to say the international community strongly demands North Korea exercise self-restraint on next month's planned rocket launch. "The planned missile launch North Korea recently announced would go against the international community's nuclear non-proliferation effort and violate U.N. Security Council resolutions," Noda said. No other major leaders mentioned North Korea's nuclear ambitions or the ballistic missile launch which the Pyongyang says will carry a weather satellite into orbit. The West says the launch is a disguised test of a long-range missile designed to reach the American mainland. North Korea said last week it would consider it a "provocation" if its "nuclear issue is placed on the agenda at the Seoul summit" and if any statement is issued against the North for pursuing such a program. It added that any provocation would amount to a declaration of war against the North and create a stumbling block in efforts to restart aid-for-denuclearization talks. Obama has said the destitute North could be hit with tighter sanctions if it goes ahead with the rocket launch, but experts doubt China will back another U.N. Security Council resolution against it. Obama told leaders the world was safer because of the steps taken to improve nuclear security, but warned that the threat of the wrong people getting hold of the materials to make a crude atomic bomb was real. "Nuclear terrorism is one of the most urgent and serious threats to global security," he said. Heralding the progress made in two years since the first such gathering of world leaders, which he hosted in Washington, Obama said the "security of the world" depended on success. It would not take much -- just a handful or so of these materials -- to kill hundreds of thousands of innocent people. And that's not an exaggeration. That's the reality that we face. Former Cold War adversaries have cooperated to lock down weapons-grade uranium and plutonium, some countries have agreed to remove all such material from their soil and poorer nations have received financial help to secure nuclear facilities. "We've come a long way in a very short time, and that should encourage us (but) that should not lead us to complacency," said Obama, in an appeal for further collaboration. We all understand that no one nation can do this alone. This is one of those challenges in our interconnected world that can only be met when we work as an international community. Noda, representing a country mired in the world's worst nuclear crisis in 25 years, also plans to tell the summit later on Tuesday what Tokyo has learned from the Fukushima disaster. An earthquake and tsunami last March knocked out external and on-site power supplies at the nuclear power plant, 240 km (150 miles) northeast of Tokyo, causing the failure of cooling systems and triggering fuel meltdowns, radiation leaks and mass evacuations.