WASHINGTON -- Local governments and business leaders shouldn't count on the federal government alone to rescue them in the event of a bird flu pandemic, the Bush administration said Thursday.

In a letter announcing an updated bird flu plan, President George W. Bush said the United States "will face this global threat" as a united front.

But Bush also writes that individual citizens are "necessary to the success" of minimizing what could be massive social and economic disruptions.

The report released Wednesday predicted a severe outbreak could take up to 40 percent of the work force off the job for a few weeks at a time.

The strategy also broke down exactly which government agency is responsible for some 300 tasks to slow the spread of the virus and dispense stockpiles of medical supplies.

A draft of the Bush plan said a worst-case outbreak could kill as many as 2 million Americans.

The draft recommends colleges be ready to select dorms to quarantine the sick.

It also suggests airlines put masks on suspect passengers and that employers place workers at least three feet apart.

However, the draft does not foresee a closure of U.S. borders.

It says that is impractical and would not be effective.

"You can't build a cage around the United States. That's impossible," Secretary of Agriculture Mike Johanns said.

Government satellites have already tracked the spread of bird flu around the world. Infected flocks fly north from Asia. They're already over Siberia and making their way into Alaska.

An annual pilgrimage is natural and unstoppable. Already, the spread of the H5-N1 bird flu virus has sped around the world faster than predicted, killing birds in 37 countries in just four months.

If infected birds arrive in the U.S. within the next few weeks as predicted, there could be outbreaks among birds in the lower 48 states by late summer.

"Worst-case scenario is that you might have an outbreak on the East Coast and somewhere in the South and somewhere on the West Coast," Johanns said.

That's why the work in Alaska is so important. It could be this country's earliest warning that an epidemic is coming.

The samples collected from living and dead birds in Alaska are being tested at 40 labs around the country.

Worldwide, the H5-N1 strain of bird flu has killed more than 110 people.