"We see today a strong focus on preventing terrorism, as well as renewed concern about naturally occurring diseases such as SARS and avian flu," he said in his opening speech.

Annan said the convention was operating in a very different environment to November 2001.

"Differences will remain. But I urge you to find, once again, creative and resourceful ways around them," he added.

The Convention prohibits the development, use and stockpiling of biological weapons.

Unlike the chemical and nuclear weapons treaties, it has little in the way of verification measures such as on-site inspections of military and private medical and pharmaceutical research laboratories.

Attempts to set up checks have been rejected by several countries, including the United States, which pulled out of negotiations on the issue shortly after President George W. Bush came into office.

Masood Khan, the Pakistani ambassador chairing the conference, said the issue of verification was likely to take a back seat in Geneva while other measures take precedence.

"I don't think it will be possible to have discussions on this," he told journalists. Nonetheless, the climate of the talks was considerably better than five years ago, he added.

The United States said Monday that it supported other reinforcements negotiated in recent years, including global disease surveillance, biosecurity measures to prevent misuse of technology, and national policing.

US Assistant Secretary of State John Rood told the conference that the major threats in the current strategic environment "come from rogue states and terrorists".

Rood reiterated that the US believed Iran and North Korea may have biological weapons in violation of their treaty commitment, while Syria -- which has signed the convention but not ratified it -- carried out research.

"The activities of North Korea, Iran and Syria are of particular concern given their support for terrorism and lack of compliance with their international obligations," Rood explained.

Several countries on Monday also highlighted the need to get more of the UN's 193 members on board the Convention. Israel, Kazakhstan and several African countries are absentees.

"We have several states that have neither signed nor ratified. We must fill that vacuum," Khan remarked.

The treaties banning biological and chemical weapons, and restricting the proliferation of nuclear weapons, are the three pillars of global protection against weapons of mass destruction.

Biological weapons are regarded as the weakest link, because of the lack of independent checks on countries and the relative ease with which medical research on viruses or bacteria can be misused by individuals.

"The advances in life sciences and biotechnology are mind boggling, they're moving at a very fast speed so you need to be vigilant," said Khan.

"Unlike nuclear weapons or chemical weapons you do not need big laboratories or an elaborate command and control system or huge facilities to develop weapons. Vigilance is the watchword," he told journalists.

On Saturday, Annan warned that biotechnology had brought the world to the threshold of a new era of both danger and opportunity, akin to the advent of nuclear power in the 1950s.

He called for a broader global drive encompassing industry, science, health experts and governments to ensure that the peaceful uses of biotechnology can be harnessed with minimal risk.

The review conference is due to end on December 8.

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