WASHINGTON (Reuter) - U.S. health experts gave a tentative endorsement Thursday to new research into the medical uses of marijuana.

Without making formal recommendations or reaching any firm conclusions following a two-day workshop at the National Institutes of Health, the chairman of the expert panel suggested that some new studies should be done.

"I'd say that for at least some of the potential indications, we feel that it looks promising enough to recommend that there would be some new controlled studies done,'' Dr. William Beaver of Georgetown University told reporters at a news conference. "Which ones, we're going to have to discuss further ... there is a rationale for looking further into the therapeutic effects of marijuana.''

Another panel member, eye specialist Dr. Paul Palmberg of the University of Miami School of Medicine, said that in at least one of his patients, smoking marijuana had been an effective treatment for glaucoma some years ago.

"(Marijuana) is definitely effective for some patients in which nothing else worked eight or 10 years ago, (but) that may not be the case now ... it needs to be looked at again,'' Palmberg said.

Under U.S. law, marijuana is illegal and has no approved clinical use. But the debate about the medical uses of the drug has intensified since last November, when voters in Arizona and California approved initiatives making it available to patients.

The Clinton administration has threatened to penalize doctors who incorporate marijuana in their practices, and advocates for medical marijuana said during the workshop that they feared politics were invading the field of science.

"This issue need not be so political, but if the Clinton administration uses these calls for more research to simply drag its feet on access for patients and access for researchers, you're going to hear a lot more contentiousness from our side,'' said Dave Fratello, an advocate of California's medical marijuana initiative.

The workshop at NIH was aimed at exploring what is known and what must be learned about marijuana's possible benefit for people with AIDS, cancer, glaucoma, multiple sclerosis and other serious diseases.

A key question for the experts was how to design an effective clinical study for smoked marijuana, notably what to use as a placebo: something that smelled, tasted and looked like a marijuana cigarette, without being one.

However, Dr. Kenneth Johnson, a neurologist at the University of Maryland Hospital, suggested that comparative studies to determine the relative effectiveness of marijuana versus other drugs in the treatment of specific symptoms of multiple sclerosis and glaucoma might be possible.

Beaver also suggested that while smoked marijuana might carry some of the same risks as smoked tobacco, using marijuana in an inhaler, similar to those used by asthma patients, could be explored.

The news conference was interrupted twice when advocates of medical marijuana use shouted out comments and were escorted out.

The expert panel will probably take a month or so to complete recommendations on what type of marijuana-related research NIH might conduct or support.

Some studies have shown marijuana can help control nausea in cancer patients, and some doctors believe the drug can give significant relief to terminally ill patients. But other doctors argue that newly available drugs do a better job.