RELIEF: Betty Hiatt, 81, smokes medicinal marijuana at her Seattle home. Having survived cancer, Crohn's disease and the onset of Parkinson's disease, the grandmother said a few puffs each morning help quell the nausea caused by her multiple prescription drugs. (Kevin P. Casey / For The Times)

A large and respected association of physicians is calling on the federal government to ease its strict ban on marijuana as medicine and hasten research into the drug's therapeutic uses.

The American College of Physicians, the nation's largest organization of doctors of internal medicine, with 124,000 members, contends that the long and rancorous debate over marijuana legalization has obscured good science that has demonstrated the benefits and medicinal promise of cannabis.

In a 13-page position paper approved by the college's governing board of regents and posted Thursday on the group's website, the group calls on the government to drop marijuana from Schedule I, a classification it shares with illegal drugs such as heroin and LSD that are considered to have no medicinal value and a high likelihood of abuse.

The declaration could put new pressure on Washington lawmakers and government regulators who for decades have rejected attempts to reclassify marijuana.

Bush administration officials have aggressively rebuffed all attempts in Congress, the courts and among law enforcement organizations to legitimize medical marijuana.

Clinical researchers say the federal government has resisted full study of the potential medical benefits of cannabis, instead pouring money into looking at its negative effects.

A dozen states including California have legalized medical marijuana, but the federal prohibition has led to an enforcement tug of war.

In California, federal agents continue to raid cannabis dispensaries, and the small cadre of physicians specializing in writing cannabis recommendations so that people can use medical marijuana has come under regulatory scrutiny.

Given the conflicts, most mainstream doctors have steered clear of medical marijuana.

The American College of Physicians' position paper calls for protection of both doctors and patients from criminal and civil penalties in states that have adopted medical-marijuana laws.

"We felt the time had come to speak up about this," said Dr. David Dale, the group's president. "We'd like to clear up the uncertainty and anxiety of patients and physicians over this drug."

Medical-marijuana advocates embraced the position paper as a watershed event that could help turn the battle in their favor.

Bruce Mirken, a San Francisco spokesman for the Marijuana Policy Project, said the ACP position is "an earthquake that's going to rattle the whole medical-marijuana debate."

The group, he said, "pulverized the government's two favorite myths about medical marijuana -- that it's not supported by the medical community and that science hasn't shown marijuana to have medical value."

But officials at the White House Office of National Drug Control Policy said calls for legalizing medical marijuana were misguided.

"What this would do is drag us back to 14th century medicine," said Bertha Madras, the agency's deputy director for demand reduction. "It's so arcane."

She said guidance on marijuana as medicine ought to come from the U.S. Food and Drug Administration, which she said is unlikely ever to approve leafy cannabis as a prescription drug.

Two oral derivatives of marijuana's psychoactive ingredient, THC, have won FDA approval, and the agency is also in the early stages of considering a marijuana spray.

An FDA spokeswoman declined to comment on the group's position and referred inquiries to a 2006 media advisory noting that the agency has never approved of smoked marijuana as a medical treatment