Unprecedented security will greet world leaders when they convene this week for the annual General Assembly debate, and the reason is shaping up to be one of the session's major themes: terrorism.

The U.S. embassy bombings in East Africa - and the larger issues surrounding them - are expected to figure prominently in comments by the 181 speakers who will begin gathering Monday for two weeks of back-to-back policy talk.Other hot topics this year are the conflict in Kosovo, the financial turmoil in Asia, Europe and Latin America and the nuclear threat in South Asia.

But it is the growing threat of international terrorism that will overshadow at least the first day of the general debate, when President Clinton will take the podium and tell the world why the war on terrorists must top its agenda.

"He wants to make it clear to the international community that the fight against terrorism is not a clash of civilizations or cultures," said Clinton's national security adviser, Sandy Berger. "The dividing line is between those who practice, support and tolerate terror and those who understand that terrorism is plain and simple murder."

The theme - which has always been a fixture of General Assembly speeches - gained prominence this year with the near-simultaneous bombings Aug. 7 at U.S. embassies in Nairobi, Kenya, and Dar es Salaam, Tanzania.

As the result of the blasts, the New York City Police Department is sealing off the main avenue in front of the United Nations for 10 days beginning Saturday night.

Trucks - presumably the kind that can carry bombs - aren't allowed within a half-mile of the building along that avenue. Massive sand trucks will block anyone from plowing through police barricades.