The donation of the treatment is part of Roche's efforts to help the world health body get prepared for a potential global human epidemic of the deadly H5N1 strain of influenza, media reports said.

The stockpile will be stored by Roche and be sent to an international airport close to the outbreak if a human pandemic develops.

Under a separate agreement, Roche has promised the WHO a further 2 million courses of the drug to be sent to build strategic stockpiles in regions where outbreaks of bird flu in humans are thought to be most likely and which are unable to afford the drug.

The moves are part of the WHO's efforts to create a global preparedness plan, and Tamiflu is regarded as the best initial defense against any pandemic resulting from a mutation of the deadly bird flu virus.

"The timing will be everything and containment has a chance to work if antivirals reach the area rapidly and no more than 21 days after the first case," Lee Jong-wook, WHO director-general, told the news conference. "We can't afford to fail."

Tamiflu, discovered by the U.S. firm Gilead, is one of two antiviral drugs recommended by the WHO as the best defense against a severe flu pandemic. The other is GlaxoSmithKline's inhaled antiviral Relenza.

Roche expects to generate up to 1.2 billion 945.6 million dollars in sales of Tamiflu in 2006 to governments around the world.