The U.S. Senate has approved legislation allocating up to $4 billion to fight bird flu by stocking up on anti-viral drugs.

The Senate measure passed Thursday also commits money to increase global surveillance of the disease.

The legislation, passed as an amendment to an unrelated military spending bill, now goes to the House of Representatives, where it faces an uncertain future.

Supporters of the measure say the time to act is now, before an outbreak occurs. U.N officials warn an avian flu pandemic could kill as many as five million people worldwide, and have urged the international community to take an aggressive stand against the disease.

Some information for this report provided by Reuters.