Fears of bird flu are receding and sales of the anti-flu drug Tamiflu have slumped. Now its maker is offering a deal to U.S. employers: Pay an annual fee and reserve enough to protect every worker if a new super-flu strikes.

The plan announced Thursday comes as the federal government also begins a new effort to encourage many businesses to stockpile anti-flu drugs in case of a pandemic. Those private stockpiles would supplement a national stockpile that contains enough doses to treat only a fraction of the population.

But stockpiling is a big upfront investment for a threat that may never arrive — and requires replacing supplies whenever drug doses expire. Roche Holding AG says its new plan would remove some of those barriers for companies otherwise interested in Tamiflu.

The U.S. government, in an unusual move, congratulated Roche on the program and helped to publicize it.

"We applaud them," said Tevi Troy, deputy secretary of the Department of Health and Human Services, which directs the nation's pandemic flu preparations. "Preparedness is a shared responsibility that extends across all levels of government and all levels of society."

Pandemics can strike when the easy-to-mutate flu virus shifts to a strain that people have never experienced. There is concern that the Asian bird flu known as H5N1 might trigger one if it acquires the ability to spread easily from person to person.

It would take months to custom-brew a vaccine against a new super-flu. So the government has stockpiled enough antiviral drugs, mostly Tamiflu, to treat 50 million people, and is urging states to purchase enough for 31 million more.

The antiviral drugs can also be used to prevent infection before a vaccine arrives. Until recently, federal health officials didn't recommend employer stockpiling for fear that there wasn't enough Tamiflu being produced to satisfy global demand during regular flu seasons, and build up the pandemic stockpiles of the U.S. and other governments.

But Roche increased global production 15-fold — and U.S. guidelines proposed earlier this month not only say that employer stockpiling is feasible, but encourage businesses to set aside enough antiviral drugs to help their workers ward off infection and stay on the job.

"Businesses that provide goods or services essential to community health, safety, or well-being have an obligation to plan and prepare for continued operations in the event of a pandemic," say the guidelines.

Roche already has sold varying amounts of Tamiflu to more than 300 U.S. businesses, said George Abercrombie, chief executive of Hoffman-La Roche Inc., the company's U.S. arm.

Under the new program, others companies could reserve Tamiflu instead of buying and storing it themselves. They would pay a yearly fee of $6 for every 10 capsules to be set aside in Roche storage and delivered within 48 hours of demand.

Upon delivery, companies would pay the going wholesale price. If a pandemic had begun, the price conceivably could spike. But Abercrombie rejected that as "a bit of a cynical view," adding, "that is not the way our company operates."

Why 10 capsules? That's the dose to treat a single ill person. To prevent infection requires a capsule a day as long as someone is potentially exposed to the virus.

In estimating how much to reserve, participating companies would have to decide how many employees they wish to cover, for either treatment or prevention — and if they'll also provide Tamiflu to workers' families. Roche has said the program requires a minimum order of 2,500 10-capsule packs, but Abercrombie said he was willing to work with smaller companies.

In January, Roche announced that sales of Tamiflu had dropped 19 percent to $1.92 billion, as government stockpiling in wake of bird-flu fears eased. Abercrombie said Thursday that production has been scaled back because of abundant supply — governments around the world had ordered 215 million courses of therapy out of 400 million available — but could ramp up again if necessary.