"It is increasingly likely that we will detect the highly pathogenic H5N1 strain of avian flu in birds within the US borders possibly as early as this year," Norton said.

As a result, the government is expanding its early warning system to deal with bird flu's eventual arrival.

"None of us can build a cage around the United States. We have to be prepared to deal with the virus here," Johanns said.

The H5N1 avian flu virus has spread across Europe, Africa and parts of Asia and killed at least 98 people worldwide since 2003. So far, it has a mortality rate of about 50 percent.

Although bird flu is hard to catch, people can contract the disease by coming into contact with infected birds, especially from bird droppings.

Scientists are concerned that the virus could develop the ability to transmit easily from person to person and trigger a worldwide pandemic which could kill millions.

Norton said the early detection plan would prioritize sampling in Alaska, where scientists believe the strain of highly pathogenic H5N1 virus currently affecting Southeast Asia would most likely spread to North America by migrating birds.

The government's expanded testing program will focus on Alaska, elsewhere in the Pacific Flyway for migrating birds and the Pacific islands, followed by the Central, Mississippi and Atlantic Flyways.

The Agriculture Department plans to collect between 75,000 and 100,000 samples from live and dead wild birds this year. Another 50,000 samples of water or feces from high-risk waterfowl habitats in the United States will also be taken.

Norton said she expected initial, so-called presumptive H5N1 results could be announced some 20 to 100 times this year but those first tests would not tell whether the virus was the deadly strain or a weaker form.

Discovery of bird flu in the United States should not be reason to panic, Johanns said, noting that positive test results could turn out to be a harmless version of the virus.

The United States has dealt three times previously -- in 1924, 1983 and 2004 -- with outbreaks in domestic poultry of other forms of bird flu.

Should US domestic poultry become infected with the high-pathogen H5N1, the Agriculture Department would act quickly to quarantine an affected area and destroy the infected flock, he said.

"Our producers have demonstrated that they will call us at the first sign of sick birds, knowing that with high-pathogen strains of bird flu we reimburse them for the birds that we destroy," Johanns said. "This is a $29 billion industry in the US and our producers are as eager as we are to protect the safety of our poultry."

Poultry properly prepared would be safe to eat because cooking with high heat kills the virus, the officials said.

The US poultry industry says it already has numerous safeguards in place to protect its flocks.

"Poultry in other parts of the world are in many cases allowed to run at large and are not protected from wild waterfowl or other birds that may be carrying viruses such as avian influenza," said Sherrill Davison, associate professor of avian medicine and pathology at the University of Pennsylvania School of Veterinary Medicine.

Meanwhile, US regulators Monday proposed banning the use of two types of human flu-fighting drugs in poultry to preserve their effectiveness for people in case of a bird flu pandemic.

The proposal would prohibit use of neuraminidase inhibitors, Roche Holding Ag's Tamiflu and GlaxoSmithKline Plc's Relenza, and the older drugs, rimantadine and amantadine, in chickens, turkeys and ducks, the Food and Drug Administration said.

While the federal government is stockpiling medicines and making other preparations, it is important for state and local governments, hospitals, businesses and schools to formulate their own plans, Leavitt said.

"Any community that fails to prepare, with the expectation that the federal government will at the last moment be able to come to the rescue, will be tragically wrong. There is no way in which 5,000 different communities can be responded to simultaneously," Leavitt said.