An abortion pill developed in France was "well-liked" and produced virtually no excessive side effects in women taking part in a small U.S. study, a researcher reported.

The results of tests on 16 American women at the University of Southern California Medical School in Los Angeles are consistent with larger studies conducted in France and elsewhere on the drug, known as RU 486."These results, from yet another continent, clearly support the existing evidence that RU 486 is safe, effective and well-liked," said Dr. David Grimes, the only U.S. researcher to test the drug.

RU 486 has been shown to be safe and highly effective for aborting early pregnancies and has been made available in France and China and is expected to become available in Britain in 1991.

The drug has not been made available to American women or U.S. researchers outside Grime's team and is not expected to be available anytime soon, due in part to opposition from anti-abortionists.

The drug, also known as Mifepristone and Mifgyne, works by blocking a hormone known as progesterone, which is needed to maintain a fertilized egg in the womb, essentially triggering a miscarriage.

In the new study, to be presented Monday at an American Public Health Association meeting in New York, Grimes used the last of a supply of the drug obtained by the Population Council in New York from the maker, Roussel UCLAF of Paris.

The study, aimed primarily at examining the drug's side effects and acceptability to women, involved women who suspected they might be pregnant because they had missed their periods.

Within 10 days of missing their periods, half the women took RU 486 while the other half were given Tylenol without knowing what they were receiving. The study is the first to compare the drug to a dummy pill.

Four women in each group turned out to be pregnant. RU 486 successfully aborted the pregnancy of three out of four of the pregnant women who took it - an effectiveness comparable to previous studies.