New York City Mayor Rudolph Giuliani warned representatives from more than 150 countries to take action against countries that support terrorism during an address to the United Nations Monday.

"The United Nations must hold accountable any country that supports or condones terrorism or you will fail in your primary mission as peacekeepers," Giuliani said in an impassioned speech before the start of a weeklong U.N. debate on international terrorism that will hear the views of more than 150 countries.

"This is not a time for further study or vague directives,'' he said. "The evidence of terrorism, brutality and inhumanity, is lying beneath the rubble of the World Trade Center less than two miles from where we meet today."

If the world's nations do not stand together in the fight against terrorism, the mayor said, the terrorists will succeed in destroying freedom, democracy and the underlying principles of the United Nations itself.

"Unanimously, we must say we will not give in to terrorism," he told representatives in the General Assembly chamber.

The meeting is the first global forum on terrorism since the Sept. 11 terrorist attacks on the World Trade Center and Pentagon, which claimed the lives of more than 6,000 people from over 60 countries.

The General Assembly was meeting three days after the Security Council unanimously adopted a resolution requiring all 189 U.N.-member nations to deny money, support and sanctuary to terrorists.

It was introduced and approved in just over 24 hours by the often plodding Security Council, reflecting Washington's wide support as it leads a global campaign to pursue those responsible for the attacks, and any nation that harbors them.

Under the resolution, all countries must make the "willful" financing of terrorism a criminal offense, immediately freeze terrorist-related funds and prevent movement of individuals and groups suspected of having terrorist connections. Nations must also deny terrorists any ``safe haven'' and speed the exchange of information, especially on the actions and movements of terrorists.

In his speech Monday, Secretary-General Kofi Annan was to emphasize that terrorism is a universal challenge which the United Nations is uniquely positioned to help address, U.N. spokesman Fred Eckhard said.

Annan has called for international cooperation to fight what he contends is an attack on all of humanity.

Since 1963, the General Assembly has adopted a dozen legal instruments to fight terrorism. But only five have been ratified by more than 100 countries and the newest — to cut off the financing of terrorism — hasn't taken effect because it has not been ratified by enough countries.

The Security Council resolution adopted Friday night incorporated key elements from these dozen legal instruments, which means they are now legally binding on all countries, whether the protocols and conventions have been ratified or not.

Eckhard said Annan would urge all nations to sign and ratify the anti-terrorism conventions "as a matter of urgent priority."

The secretary-general was also expected to warn against the even more dangerous threat of terrorists using biological, chemical and nuclear weapons and call for action to prevent the use of weapons of mass destruction.

The General Assembly postponed its annual ministerial meeting because of the attacks, so the speakers at the terrorist debate will be primarily U.N. ambassadors, although a few foreign ministers are still expected to attend.

Giuliani has been praised worldwide for leading a massive search and rescue effort and later a cleanup at the site of the collapsed World Trade Center towers in New York.

Giuliani is the first New York City mayor in nearly 50 years to address the General Assembly, assembly spokesman Jan Fischer said. Mayor William O'Dwyer addressed U.N. delegates in 1949, when the cornerstone for the present U.N. headquarters was laid, and Mayor Vincent R. Impellitteri spoke at the first General Assembly meeting in the new 39-story building in 1952.

The Associated Press contributed to this report.