WASHINGTON - Fears of bird flu are slumping and so have sales of the anti-flu drug Tamiflu. 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 part of the population.

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