David Nabarro, the UN coordinator for avian and human influenza, said "it will take six months to build up a stockpile of vaccines," but health authorities are worried that might be too long if a pandemic flu strain emerges.

"We will need to have vaccines much more quickly than six months," Nabarro said, adding that the World Health Organization and governments are exploring how to "pull together vaccine manufacturers" to see if it can be done more quickly.

Looking at Options

"The World Health Organization as we speak is looking at options to get a scaling up of vaccine production capacity," Nabarro said.

UN experts briefed journalists at the UN Food and Agriculture Organization about the global bird influenza situation.

Turkey and Romania culled thousands of birds Monday as a precaution after suspecting bird flu in their flocks.

There is no confirmation that birds in Romania and Bulgaria have been infected, and experts in Turkey will need a couple more days for definitive results on birds there, UN officials said.

Nabarro said that because viruses mutate, it is not known how efficient existing vaccines will be in case of a human pandemic.

Focusing on Prevention

Louise Fresco, an agriculture official at the Rome-based Food and Agriculture Organization, said experts are focusing for now on prevention.

She said initially that the UN agencies would be seeking US$175 million (€144.77 million) -- "a fraction of what is needed" -- for initial efforts aimed at combatting bird flu and preventing a possible jump to people.