America's prescription drug supply is the safest in the world, but attempts to counterfeit drugs are increasing and becoming more sophisticated, the head of the Food and Drug Administration (search) said Wednesday.

"This is a real public health threat," Mark McClellan told a meeting of the pharmaceutical industry.

The FDA commissioner called on drug manufacturers and distributors to help develop fresh and innovative ideas for keeping the drug supply secure.

Organized crime is becoming attracted to prescription drug sales because there is money to be made by faking costly medications, McClellan said.

In addition, some counterfeit drugs come from foreign sources, raising concerns as Americans increasingly look outside the United States for less costly drugs.

McClellan toured a packed trade show displaying a range of technologies aimed at preventing the sale of counterfeit drugs. Manufacturers showed off tiny bar codes that can be painted on pills, tamper-resistant packaging sporting hard to copy holograms and even tiny DNA-encoded microchips.

"What surprises me is how many technologies there are," McClellan said. Many of the ideas come from other industries and have not been previously used on pharmaceuticals, he said.

While no one argues against the need for safe and effective medicine, drug importation has become a complex political issue because many drugs can be bought cheaper in other countries, ordered by mail or over the Internet. Imports are the source of many counterfeit drugs.

The FDA says it cannot guarantee the safety of imported products, while critics charge the agency is trying to undermine congressional efforts to let people buy less costly drugs.

The pharmaceutical industry also launched a major effort to block drug import legislation, spending $8.5 million on lobbying this year alone.

FDA convened Wednesday's meeting to seek comment and guidance on ways to prevent counterfeit pills from being sold to Americans.

Among possibilities to help defeat counterfeiters are requiring manufacturers to ship pills in smaller quantities, making it less profitable to substitute counterfeits, or using high-tech gadgets such as hidden transmitters or chemical tags to help assure pharmacists medications are genuine.

The agency's counterfeit drug task force, formed in July, says it will take multiple strategies because it takes no longer than a year or two for criminals to crack and copy many anti-tampering measures, such as holograms on packaging.

When drugs are bought from regular licensed pharmacies, the chances of getting a counterfeit are less than 1 percent, McClellan has estimated.

Buying drugs over the Internet can increase the risk, however, and counterfeits are sneaking into regular drugstores more often. The FDA has investigated about 20 counterfeit cases a year since 2000, compared with five a year in the 1990s.

The FDA reported in September that of 1,153 imported drugs checked by FDA and Customs agents, 1,019 were found to be illegal. They included drugs that had been withdrawn from the U.S. market, animal drugs never approved for human use, counterfeit drugs, drugs with dangerous interactions, drugs with dangerous side effects and narcotics.

The House passed a bill in July that would require the Department of Health and Human Services to set up a system to allow importation of FDA-approved drugs from FDA-approved facilities in Canada, the European Union and seven other nations.

The bill faces an uncertain future in the Senate, however, and the Bush administration said the bill was dangerous legislation.