US President George W Bush has unveiled a $7.1bn (£4bn) national strategy to tackle a possible flu pandemic, with a focus on improving vaccines.
The lethal strain has already spread from Asia to Europe
Mr Bush said the US was "likely" to face a pandemic at some point, whether caused by a strain of Asian bird flu, or another super-flu strain.
At the heart of the plan is a request for $2.8bn to accelerate development of vaccines using cell-culture technology.
Democrats had criticised Mr Bush, saying the US has been slow to prepare.
The BBC's Jonathan Beale, in Washington, says concern has been all the greater because of the slow response to Hurricane Katrina, and the president wanted to be seen to be taking action now.
The H5N1 strain of bird flu has killed more than 60 people in South East Asia since late 2003.
'Could spread quickly'
"Avian flu has developed some of the characteristics needed to cause a pandemic," the president told the US National Institutes of Health in Maryland.
H5N1 BIRD FLU VIRUS
Principally an avian disease, first seen in humans in Hong Kong in 1997
Almost all human cases thought to be contracted from birds
Possible cases of human-to-human transmission in Hong Kong, Thailand and Vietnam, but none confirmed
"The virus has demonstrated the ability to infect and produce a fatal illness in humans.
"If the virus developed the capacity for sustained human-to-human transmission, it could spread quickly around the world," he added.
The US must be prepared to detect outbreaks anywhere in the world, stockpile vaccines and be ready to respond at federal, state and local levels in the event a pandemic reaches the United States, Mr Bush said.
The strategy entails:
- $1.2bn for the government to buy enough doses of the vaccine against the current strain of bird flu to protect 20 million Americans
- $1bn to stockpile more anti-viral drugs that lessen the severity of the flu symptoms
- $2.8bn to speed the development of vaccines as new strains emerge, a process that now takes months
- $583m for states and local governments to prepare emergency plans to respond to an outbreak
To equip Americans with accurate information on how to protect themselves and their families, the government is launching a website: www.pandemicflu.gov.
Tens of millions of birds have been destroyed around the world since the deadly strain of the virus was first detected in 2003.
The disease has also been detected in birds in Russia, Croatia, Turkey and Romania.
While more than 60 people have died of the virus, there is only one suspected case of the disease being passed from human to human.
On Monday, Canada said it had discovered a strain of bird flu among healthy wild birds in the provinces of Quebec and Manitoba.
An official said it would take a number of days to determine whether the birds are carrying the strain of the avian flu that is lethal to humans.