Pledging to rally U.S. science and technology against "the greatest danger of our time," President Bush today signed into law a $5.6 billion bill aimed at bolstering the nation's defenses against biological, chemical and nuclear terrorism.

In a ceremony in the White House Rose Garden, Bush said the legislation, the Project Bioshield Act of 2004, "will help America purchase, develop and deploy cutting-edge defenses against catastrophic attack."

He said the new law "is part of a broader strategy to defend America against the threat of weapons of mass destruction."

The legislation, which took 18 months to reach his desk despite broad bipartisan support in Congress, enables the government to purchase and stockpile vaccines, expedite research on medicines to combat bioterrorism and, in a crisis, distribute new drugs that have not been approved by the Food and Drug Administration.

The House overwhelmingly approved the plan, but it bogged down in the Senate over various provisions, including expedited federal contracting procedures and disclosure guidelines for vaccinating military personnel. It eventually passed the Senate by a vote of 99 to 0 in May after the objections were resolved.

Before signing the bill, Bush said the Sept. 11, 2001, terrorist attacks had demonstrated the determination, but not the full ambitions, of America's enemies.

"We know that the terrorists seek an even deadlier technology," Bush said. "And if they acquire chemical, biological or nuclear weapons, we have no doubt they will use them to cause even greater harm."

He said, "We refuse to remain idle while modern technology might be turned against us; we will rally the great promise of American science and innovation to confront the greatest danger of our time."

Bush said Project Bioshield improves the nation's defenses by authorizing $5.6 billion over 10 years "for the government to purchase and stockpile vaccines and drugs to fight anthrax, smallpox and other potential agents of bioterror." He said the Department of Health and Human Services has already taken steps to buy 75 million doses of an improved anthrax vaccine for the Strategic National Stockpile and is moving forward with plans to acquire "a safer, second-generation smallpox vaccine, an antidote to botulinum toxin and better treatments for exposure to chemical and radiological weapons."

The law also "gives the government new authority to expedite research and development on the most promising and time-sensitive medicines to defend against bioterror," Bush said. He said HHS Secretary Tommy G. Thompson will put the new powers to use today by directing the National Institutes of Health to launch initiatives to accelerate the development of new treatments for victims of biological and radiological or nuclear attacks.

Under the new law, Bush said, the Food and Drug Administration "will be able to permit rapid distribution of promising new drugs and antidotes in the most urgent circumstances."

Staff writer Charles Babington contributed to this report.