Promising medical research into diseases ranging from breast cancer to AIDS is suffering because of a goverment ban on the French abortion pill in the United States, doctors and a congressman charged.

Medical researchers and Rep. Ron Wyden, D-Ore., sharply criticized the Food and Drug Administration during a contentious three-hour hearing Monday on the status of the controversial drug RU 486."In the name of taking some kind of symbolic action . . . critical medical research is being derailed," Wyden said. "Americans are going to suffer needlessly due to this position. I think it's very irresponsible."

FDA officials defended their decision to issue an alert that RU 486 could not be brought into the country for personal use because it can cause serious side effects like bleeding and may be used without a doctor's supervision.

"The import alert was to try to protect individual citizens in this country," said Ronald Chesemore, the FDA's associate commissioner for regulatory affairs. The alert, similar to that previously issued for nearly 60 other drugs, placed no limitations on importing the drug for research, he said.

RU 486 has been shown to be safe and effective for inducing abortions early in a pregnancy, allowing women to avoid surgical procedures. The drug has been made available for that use in France and other countries.

But the drug has not been approved in the United States. The drug's manufacturer, Roussel-Uclaf of Paris, has no plans to seek approval, in part because of strong opposition from anti-abortionists.

The FDA does, however, make exceptions in rare cases for individuals to bring small quantities of unapproved drugs into the country for their own use. But in June 1989 the agency issued an "import alert" announcing RU 486 would not be permitted in that way because of concerns over "safety of the user."