U.N. Secretary-General Kofi Annan has proposed an international treaty outlawing terrorism. Mr. Annan unveiled a comprehensive anti-terror strategy at a conference marking the one-year anniversary of the deadly train attacks in Madrid.

Speaking to a gathering of leaders and terrorism experts from 50 countries, the secretary-general said the world must move quickly to deny terrorists the means to launch a nuclear attack that could cause international chaos. He said it is time to recognize that the threat of nuclear terrorism is real.

"Nuclear terrorism is still often treated as science fiction," he said. "I wish it were. But unfortunately we live in a world of excess hazardous materials and abundant technological know-how in which some terrorists clearly state their intention to inflict catastrophic casualties."

Mr. Annan outlined a five-point strategy for combating terrorism. He urged U.N. member states to put aside squabbles over the definition of terrorism that have blocked agreement on a global treaty, and allow the United Nations to take the lead role in the fight.

"The U.N. must be at the forefront at fighting against terrorism and first of all in proclaiming loud and clear that terrorism can never be accepted or justified in any course whatsoever," he said. "By the same token, the U.N. must continue to insist that in the fight against terrorism, we cannot compromise on core values - in particular, human rights and the rule of law must always be respected. As I see it, terrorism is a direct attack on human rights and the rule of law. If we sacrifice them in our response we will be handing victory to the terrorists."

In an implicit criticism of the U.S.-led war on terror, Mr. Annan said it was regrettable that "many measures which states are currently adopting to counter terrorism infringe on human rights and individual freedom."

The Madrid conference is part of Spain's observance of the train bombings last March 11. Those attacks, believed to have been carried out by Islamic extremists killed nearly 200 people and injured 1500 others.

Spain will hold a day of mourning for the victims Friday. Church bells will ring at the exact time the 10 bombs exploded on the four trains.