Reagan administration officials say "ethical and legal" questions are behind their ban on the use of tissue from aborted fetuses in experiments at the National Institutes of Health.

"The morality and science are all mixed together," Dr. Robert E. Windom, assistant secretary of health at the Department of Health and Human Services, said in Friday's Washington Post."They need to be evaluated before we rush ahead. We just can't afford to move too hastily on this," he said.

Windom's decision last week was prompted by an NIH proposal to implant fetal tissue into patients with Parkinson's Disease, the newspaper reported.

Thousands of aborted fetuses are used each year in research on Parkinson's disease, juvenile diabetes and leukemia. Researchers told the newspaper the special composition of the tissue holds promise for treatment of the diseases.

Researchers contacted by the Post expressed dismay at the decision.

"NIH sets the pace, and this will cripple fetal research in the United States," said Dr. Bernard Liebel, professor of medicine at the University of Toronto.

"It is an extraordinarily valuable research tool with immense potential. Depriving research scientists of this material is a great disservice to humanity," he said.

"If the parents were a part to the killing, they have no right to assign organs to another person," said Dr. John C. Willke, president of the National Right-to-life Committee. "That is desecration of a corpse."

Windom, in a letter to NIH Director James B. Wyngaarden, said he was "withholding my approval of the proposed experiments" due to "ethical and legal" questions that had not been addressed satisfactorily. He directed Wyngaarden to create an outside advisory committee to examine such questions, the Post said.