The U.S. Senate unanimously (99-0) approved legislation Wednesday that would fund the research, production and stockpiling of vaccines and antidotes in preparation for a potentially devastating bioterrorism attack.

The $5.6 billion bill would encourage the public and private sectors to research and develop bioterrorism countermeasures.

It would also accelerate the approval process for antidotes, and allow the government in an emergency to distribute certain treatments before they are approved by the Food and Drug Administration (FDA).

In the aftermath of the discovery of sarin in Iraq in recent days, and the discovery of anthrax and ricin-laced letters here on Capitol Hill in recent years, the Senate was quick to approve the legislation.

The Senate's top Republican, Senator Bill Frist, who is a medical doctor and author of a book on bioterrorism, said the bill will assure drug companies that there will be a market for new products, which under normal circumstances would have little market value. ?The bill provides the private sector with new incentives to invest in research and development of biomedical countermeasures that otherwise would simply not have the business potential,? he said.

Senator Frist's office received a letter laced with ricin last year. The case is under investigation, as is an anthrax-laced letter sent to Senator Tom Dashcle's office, the Senate's top Democrat, in 2001.

The House of Representatives passed similar legislation last year.

Differences between the House and Senate versions will have to be reconciled before a final bill is sent to President Bush, who has long pressed Congress for such legislation.