Policymaking delegates of the AMA, the nation's largest doctor's group, adopted the measure without debate after discussing the issue Sunday.
"It makes a stance for science," said Dr. Michael Goldrich, incoming chairman of the committee that drafted the cloning report.
The proposal focused on a laboratory procedure designed to create embryos to cultivate their stem cells, which are master cells that can potentially grow into any type of human tissue. Scientists believe such cells could potentially be used to treat a wide range of human diseases.
Such early embryos would be discarded when they consist of only a few cells, but they could theoretically develop into a human if implanted into a woman's uterus.
The AMA's Council on Ethical and Judicial Affairs submitted the proposal with hopes that it would become official AMA policy.
The proposal received wide support from doctors and medical groups including the American Society for Reproductive Medicine. But some adamantly opposed it with arguments reminiscent of the nationwide abortion debate.
Calling embryo cloning for research purposes medically ethical is "totally inappropriate ... when a number of us believe that human beings start with two cells," said Dr. John McMahon of Helena, Montana.
The proposal echoed recommendations from a National Academy of Sciences panel last year, which advocated a government ban on cloning to produce humans but said cloning for research should be allowed.
The U.S. House earlier this year passed a Bush administration-backed measure that would ban both types of cloning. The measure hasn't been acted on in the Senate.
In other action Tuesday, the AMA agreed to investigate the ethics of letting drug company sales representatives sit in on patients' visits with their doctors.
Drug companies sometimes pay doctors up to $500 a day to allow their reps to observe patient visits — a practice they maintain is educational but which opponents say violates patients' privacy.
The AMA opposed the practice unless the patient has clearly consented without coercion and asked for guidelines to make sure patients are not coerced.
By Lindsey Tanner