"Companies would be hesitant to develop something if they didn't know what was at the end of the rainbow," Fauci said. "If you deliver the product, we will guarantee you get money."

Dozens of companies backed the new program. But, executives say, Bioshield doesn't remove all the uncertainties of developing the drugs. They complain that it does not offer complete liability protection should a drug have adverse effects on patients or fail to protect them against a pathogen, which could lead to lawsuits. It also doesn't eliminate the chance that another company will develop a better product that the government wants more.

Few companies have shown much enthusiasm for diverting staff and money from programs to develop drugs, such as cancer and cholesterol treatments, with bigger and more established markets. Of about 1,000 U.S. biotechnology companies, about 100 are working on biodefense projects, according to the Biotechnology Industry Organization, an industry trade group.

Human Genome Sciences' anthrax treatment is being tested for safety in humans. But because it would be unethical to expose people to deadly pathogens, it cannot be tested for effectiveness. Companies can't know if a drug can protect people from a given biological agent until after an attack.

"Until the liability question is solved, we're not going to see big drug companies come to the table," said Frank M. Rapoport, who represents vaccine maker Aventis Pasteur SA. "They have too much to lose."

Other Washington companies working in biodefense say Bioshield is unlikely to substantially alter their business plans.

Two of them, Dynport Vaccine Co. of Frederick and GenVec Corp. of Gaithersburg, are working on vaccines for the military and said they are exploring the possibility of applying for Bioshield money.

Cambrex Corp. of East Rutherford, N.J., which has offices in Baltimore and Walkersville, Md., and Invitrogen Corp. of Carlsbad, Calif., which this year bought BioReliance Corp. of Rockville, perform contract testing and manufacturing services for companies in biodefense. Both expect new clients as smaller biotechnology companies, with limited space and staff, apply for Bioshield funding.

Still, C. Robert Eaton, president of MdBio Inc., a Maryland trade group for biotechnology companies, said, "I don't think companies are going to turn on a dime to start chasing this money."

Congress rejected industry efforts to include in the Bioshield bill stronger incentives such as research and development tax credits, the extension of existing patents and stronger liability protection.

But Fauci said he expects Congress to address the industry's biggest concerns, such as liability. "Bioshield does not solve all the disincentives a company may have to get involved," he said. "But it's a very good start."