The world's biggest science festival opens on Thursday in Washington DC.

Research leaders from Africa to Asia are among more than 5,000 international delegates attending the annual meeting of the American Association for the Advancement of Science (AAAS).

Guests include Mozambique's new minister of higher education, science and technology, and the US Secretary of State Madeleine Albright.

The theme of this year's meeting is a grand one: "Science in an Uncertain Millennium".

According to the president of the AAAS, Professor Stephen Jay Gould, the expo is a chance to discuss both the glories and problems of science.

"We are all part of one the greatest intellectual adventures in human history - the growth, stunning excitement and occasional peril endangered by the enterprise called science," he told reporters.

Strong arguments

Delegates will hear about some of the very latest research in areas such as cancer therapy, climate change, and the race to decode the human genome.

The five-day meeting is also a chance for scientists and policy makers from around the world to share information and forge closer links.

But there will be plenty to excite the public and much of it will provoke strong arguments:

• Should genetic engineers be allowed to alter human DNA so that the changes are inherited?
• Will space travel really become possible for everyone in the near future?
• Can the cyber-terrorists, currently wreaking havoc on the web, be beaten?
• Will the scourge of landmines be banished with new technology?

Surprises are also in store with news that nicotine could be good for you and that primates may have invented society.

This annual meeting of the AAAS is the latest in a series that began in 1848.