WASHINGTON — A triple-punch combination of an experimental new AIDS drug and two others already on the market is by far the most potent treatment yet for people infected with the deadly virus, researchers reported Monday.

The therapy does not cure AIDS. At best, it will slow and perhaps stall the disease for long periods. Even this could be a significant advance, since currently available virus medicines do little to extend AIDS patients’ lives.

The treatment involves one of a new class of drugs called protease inhibitors and is still in early stages of human testing. Nevertheless, AIDS researchers who have seen many promising initial results go sour in the past are enthusiastic about the latest findings.

“It’s wonderfully exciting. It’s a milestone,” said Dr. Gerald Friedland of Yale University.

The key to the new combination is indinavir, a still-experimental protease inhibitor developed by Merck & Co. It is combined with the standard AIDS medicines AZT and 3TC.

Dr. Roy Gulick and colleagues from New York University gave the combination to 26 patients. After six months, they could find no measurable trace of the AIDS virus in 24 of them. Their treatment is continuing, but researchers say it is still too soon to know how long this effect will last.

Gulick planned to present his results in detail Thursday at the annual Conference on Retroviruses and Opportunistic Infections, an AIDS meeting sponsored by the Infectious Disease Society of America. However, Dr. Emilio Emini of Merck released some of the findings at the meeting Monday at a standing-room-only session on protease inhibitors.

“This is the best response of any anti-retroviral therapy that has been seen to date,” said Gulick, and several other AIDS experts at the meeting agreed.

The first protease inhibitor to reach the market was saquinqavir, a Hoffman-LaRoche drug approved last month by the U.S. Food and Drug Administration. However, experts believe that indinavir and ritonavir, another protease inhibitor being tested by Abbott Laboratories, are considerably more powerful.