AUCKLAND, New Zealand - The World Health Organization still lacks about half the funds it needs to help countries fight bird flu, the acting director-general said Tuesday.

"We have still not been able to fill the gap. There's still a shortfall," Anders Nordstrom, acting head of the Geneva-based U.N. health agency, told The Associated Press. "We still are able to respond when there are outbreaks, but to be able to really work with countries to build up good surveillance systems and information systems, we do need more resources."

Nordstrom said WHO needs US$90 million to US$100 million over a two-year period, but has only received about half of that amount. He said countries themselves also need to come up with more funding to help strengthen surveillance and rapid response systems within their borders.

Nordstrom spoke on the sidelines of the annual WHO Western Pacific regional meeting in Auckland, New Zealand, which brings together health officials from across the Asia-Pacific to set the organization's strategic agenda for coming years.

Bird flu and the fear of a pandemic has remained a top item on the meeting's agenda for the third straight year. Experts fear the H5N1 virus will mutate into a form that spreads easily among people, potentially sparking a pandemic. So far, most human cases have been linked to contact with infected birds.

As the cooler months approach, Nordstrom said another spate of poultry outbreaks and human infections will likely emerge, but added that many countries have made great strides to prepare and beat back the virus.

"I think we will see the same pattern," he said. "If we look back three years, we have had a peak starting in January and February, and what has changed over the last three years is that we have seen cases in more and more countries both in birds and in human beings."

Representatives from nearly 20 countries pledged their support and vowed to continue working together to prepare for a worst-case scenario, with several Pacific island nations requesting help in monitoring migratory birds.

Delegates from Australia and South Korea said they were planning exercises this year to test their pandemic preparedness and raise public awareness.

Singapore Health Minister Khaw Boon Wan said his city-state has already held two exercises and encouraged more countries to set up mock scenarios to practice.

"I think almost certainly if there were to be a crisis, very likely it would originate from our part of the world," he said. "So our region should really be exemplary in showing the rest of the world how you can avoid this crisis and should it happen, how to minimize it."

The H5N1 virus has killed at least 144 people since it began ravaging Asian poultry stocks in late 2003.