Asia's bird flu virus is resistant to key anti-influenza drugs, and an effective vaccine is probably more than six months away, the World Health Organization (search) said Sunday, as Indonesia confirmed it had become the seventh country in the region with an outbreak.

The WHO said it would launch a massive funding appeal to help Asian nations destroy millions of chickens in an attempt to stem the disease. Experts warned that if the mass slaughter is improperly carried out, it might only help the virus' jump from fowl to humans.

In Indonesia, bird flu has affected millions of chickes, said Sofjan Sudardjat (search), a senior Indonesian Department of Agriculture official. But the virus has not crossed over to humans, he said.

Vietnam and Thailand are the only countries this year where humans have caught the avian flu, with six confirmed deaths in Vietnam and one suspected fatality in Thailand.

But the virus has hit millions of chickens in five other countries as well — raising concerns it might mutate, link with regular influenza to create a form that can be transmitted from human to human, fostering the next human flu pandemic.

World Health Organization spokesman Dick Thompson (search) warned that the H5N1 virus in humans appears to be resistant to amantadine and rimantadine, the cheaper anti-viral drugs used to treat regular influenza.

"This is a disease that's appearing in the developing world. So what you want is affordable drugs," said Thompson in Geneva. "Should this move from human to human — and it hasn't yet, I want to stress that — then it's going to be a real challenge."

Last week, WHO influenza chief Dr. Klaus Stohr said other anti-viral drugs still appeared to work against the bird flu virus in humans.

WHO also reported that the virus, thought to be highly adaptable, had already mutated — setting back hopes for creating a vaccine, which the organization had said might be ready within four weeks.

"I don't think we're looking at a workable vaccine within six months. That's too late for the influenza season in Asia but it would be available," regional WHO spokesman Peter Cordingley told The Associated Press in the Philippines.

"It could be available for next winter's flu season ... It's not promising this year," he added.

On its Web site, a WHO statement said new strains that haved appeared were "significantly different from other H5N1 strains isolated in Asia in the recent past, thus necessitating the development of a new prototype strain for use in vaccine manufacturing."

Asia is on a region-wide health alert, with governments slaughtering millions of chickens to contain outbreaks in Thailand, Vietnam, Cambodia, South Korea, Japan and Taiwan.

On Sunday, China — which has so far reported no cases of bird fly — banned all poultry from Thailand and Cambodia, two days after cases of the virus were confirmed in both Southeast Asian nations.

China is eager to show its resolve in proactively battling bird flu, particularly after last year's severe acute respiratory syndrome epidemic brought the communist government under criticism for its initial guarded response.

Hundreds of Thai soldiers, wearing rubber gloves, boots, colorful shower caps and safety masks, helped clear farms of chickens in Thailand's Suphanburi province — the area hardest hit by an outbreak of bird flu.

"It's not dangerous, but don't be neglectful," Deputy Agriculture Minister Newin Chidchob said as he briefed soldiers lined up at the village hall. "The safety masks may be uncomfortable because you're not used to them, but don't even think of taking them off."

Some 450 troops were joined in the operation by 60 prisoners from the provincial jail. In Thailand, prisoners are sometimes called out to dig ditches, repair sewage works and perform other manual public service labor.

WHO backs a poultry cull in affected countries as the best way to wipe out the disease. But Thompson said that if the mass slaughter is not funded and handled properly it could make things worse, so the U.N. organization will appeal for international donations to ensure it's carried out correctly.

"Safety's the key. You don't want the virus to start mixing in humans. If you send a lot of humans in to do culling you'd be exposing them," unless they wear protective clothing and goggles — something many poor nations can ill-afford, Thompson said.

"It's going to be an enormous burden on the developing world to do safe culling," he said. "We're also going to be asking for assistance for reimbursement to pay backyard farmers when we ask them to kill off their investment in their poultry stock and give them a reasonable incentive to do that."

Thai officials, following weeks of denial, acknowledged the virus' presence this week after poultry farmers claimed not enough was being done to stop the disease from spreading from nearby countries.

In a weekly radio address, Thai Prime Minister Thaksin Shinawatra acknowledged Saturday that the onset of the virus in Thailand could devastate the country's chicken export sector — the world's fourth largest.

Thailand shipped about 500,000 tons of chicken worth $1.3 billion in 2003. But the 15-nation European Union and Japan — Thailand's biggest markets for poultry — and several other countries also have announced poultry bans.