Roche AG says it will build a U.S. plant to make more of its anti-bird flu drug Tamiflu, as demand for the drug is far outstripping Roche’s ability to make it.

Some 40 countries are scrambling to create Tamiflu stockpiles to treat millions if a pandemic occurs. U.S. officials have called for a Tamiflu stockpile to treat 20 million Americans, yet have only enough pills on hand to treat 4.3 million people.

Roche, the sole manufacturer of Tamiflu, said Tuesday that it was seeking other companies to help speed production. Sales of the once-obscure drug’s sales have skyrocketed from $76 million in 2001 to an estimated $700 million this year.

Roche refused to say where its new plant would be located, citing security concerns.