United Nations agencies said Saturday Vietnam's bird flu outbreak, which has killed 14 people in the country, could take years to eradicate, as China reported four new confirmed outbreaks of the disease.
Thailand, where five people have been killed by the virus, meanwhile said it aimed to conquer its bird flu crisis by the end of the month.
Vietnamese officials have also said they aim to declare the country free of the disease by the end of February, and have suggested poultry sales could be allowed to resume in March.
The outbreak of the H5N1 strain of the bird flu has led Vietnam to cull 35 million chickens and inflicted devastating losses on the local poultry farmers.
But the World Health Organisation and the Food and Agriculture Organisation (FAO) both said hopes for a quick recovery of Vietnam's poultry industry were premature.
"We believe the outbreak won't be eradicated for several months, probably years," WHO spokeswoman Maria Cheng said.
Ways of effectively controlling the outbreak were only now being put in place, said FAO representative in Hanoi, Anton Rychener.
"We are right now only starting the engine to control the outbreak," he said. "It will be long. I am not sure the government has admitted this reality."
On Friday the World Bank indicated it was ready to lend Vietnam 10 million dollars to help its poultry industry recover from the crisis and "make sure, should it happen again, that it could have a better response".
The FAO estimates some 80 million chickens and other fowl have now been culled to contain the epidemic, which has struck 10 Asian nations and the United States.
Despite regional efforts at containment, the spectre of a spreading epidemic loomed large as Beijing announced four new confirmed bird flu outbreaks, one of them in the city of Zhuhai close to Macau, state media reported.
The other confirmed outbreaks were in the cities of Yangjiang and Maoming, both southern Guangdong province, as well as in Nanning city in neighbouring Guangxi region, Xinhua news agency said.
The new report brings the total in China to 34 confirmed and 13 suspected outbreaks.