China announced Tuesday that it will carry out a massive poultry vaccination campaign to combat the spread of bird flu in the world's most populous nation.

Jia Youling, chief veterinary officer in the Agriculture Ministry, told the official New China News Agency that as many as 14 billion chickens, ducks and geese -- China's total stock of poultry -- could be subject to the vaccination. He did not explain how such an unprecedented nationwide campaign would be mobilized but emphasized the Chinese government's eagerness to check the disease.

In response to questions later, Jia said on the official People's Daily Web site that some large-scale industrial poultry farms would not have to resort to vaccination because, unlike small farms, they are able to isolate their stocks and guarantee they are free of disease.

The government's attitude toward acknowledging bird flu outbreaks and taking decisive steps to deal with them has been watched closely by the World Health Organization and other international groups trying to prevent a deadly outbreak in Asia, where 64 people have died from the disease since 2003. Bird flu is lethal, but has so far not changed into a form that is highly contagious from human to human.

The spread of SARS -- severe acute respiratory syndrome -- in China two years ago, international health organizations charged, was worsened by attempts at several levels of the Chinese government to conceal the seriousness of the disease among China's 1.3 billion people.

Officials in Vietnam, meanwhile, said they have decided to order residents of Ho Chi Minh City and Hanoi, the country's two largest cities, to get rid of all their poultry to prevent the disease from spreading within urban populations. China announced Monday that it plans to send 45 tons of vaccine to Vietnam, where a number of outbreaks and human infections have been reported.

A dozen outbreaks of the H5N1 strain of avian flu have been reported in China during recent months but all have been contained by culling stocks and isolating the infected areas, government officials say. There have been no confirmed cases of human infection, according to the officials, although several people in China have fallen ill with symptoms that have lead doctors to suspect they may have contracted the disease.

WHO has dispatched a six-member team to China to help conduct tests to determine the source of the illnesses. A senior Agriculture Ministry official, quoted by the Hong Kong-based South China Morning Post, said that a 9-year-old boy in Hunan province had received a tentative diagnosis of bird flu, but that a final determination would be made after further tests. The boy's sister, 12, died Oct. 17 after running a high fever, the official New China News Agency said.

Jia, who announced the nationwide vaccination campaign late Tuesday night, said the government would pay for most of the costs. He did not detail how long the campaign would take or how it would be organized. Millions of birds already have been vaccinated, he noted. But the new campaign he described would imply an unusually concerted mobilization of resources, officials and people.

China produces a number of avian flu vaccines for poultry, although international health experts say they do not know the extent of production capacity.

Jia noted the difficulties in carrying out the vaccination project, emphasizing the informal nature of much of China's poultry industry. Although it produces 20 percent of the world's poultry, the industry includes millions of farmers who raise a few chickens and ducks in their back yards or around a nearby pond and who tune in only vaguely to what is happening around the world.

"China has a lot of backyard-bred poultry," he told the official news agency. "Some farmers pay no attention to the disease."