Federal Trade Commission Chairman Jon Leibowitz said Friday that U.S. antitrust enforcers may consider revising their 17-year-old guidelines for determining whether proposed business mergers are anticompetitive.

Leibowitz, speaking at an American Bar Association conference in Washington, also said that stopping pharmaceutical patent settlements that delay the entry of generic drugs is one of the FTC's highest priorities.

"These deals are anticompetitive," he said.

Advocates for revising the merger guidelines, published in 1992, say the government's written merger policies no longer accurately reflect the real-world practice of how U.S. antitrust agencies review mergers, which creates uncertainty for companies considering M&A transactions.

Critics also say the merger-guideline numbers used for measuring business-market concentration are too low and flag too many mergers as having possible anticompetitive effects.

Leibowitz, appointed by President Barack Obama last month to the FTC chairmanship, said Friday, "We may want to revisit the merger guidelines, which are badly in need of updating."

He said he would discuss the issue with Obama's nominee to be the chief competition enforcer at the Justice Department, Christine Varney, once she is confirmed.

The FTC and the Justice Department share antitrust regulatory authority.

On the issue of generic-drug competition, Leibowitz said the FTC continues to bring lawsuits challenging deals in which brand-name drug makers pay their generic competitors to delay the introduction of competing generic drugs. "We have more investigations in the pipeline," he said.

But to date, the commission has not fared well against drug makers in court. In one closely watched case, the FTC failed in its challenge to an agreement between Schering-Plough (SGP) and generic companies that delayed competing versions of K-Dur 20, a potassium supplement.

Last month, the FTC sued three drug makers in a California federal court, alleging that Brussels-based Solvay Pharmaceuticals Inc., the maker of the testosterone drug AndroGel, entered into an illegal agreement with generic drug companies Watson Pharmaceuticals Inc. (WPI) and Par Pharmaceutical Cos. (PRX) to delay the introduction of a generic competitor.

Leibowitz said he was hopeful that Congress would pass legislation to bar the settlements. He said he expects legislation on the issue to be re-introduced by lawmakers next week.

-By Brent Kendall, Dow Jones Newswires; 202-862-9222; brent.kendall@dowjones.com