A Food and Drug Administration panel yesterday recommended approval of U.S. sales of the cervical cap, a barrier contraceptive comparable to the diaphragm but deemed more convenient.

The recommendation to FDA Commissioner Frank E. Young is contingent on agreement by Lamberts Ltd., British manufacturer of the Prentif Cavity-Rim cervical cap, to conduct further study of a possible link between its use and a small number of cervical abnormalities seen on PAP smears after three months of use. Dr. Lillian Yin, chief of the FDA division on obstetrical and gynecological medical devices, said she believes that the agreement would be made soon and that final FDA approval could be granted in mid-April.

The cervical cap has been used widely in Europe for decades, and mention of similar devices has been found in ancient Egyptian scrolls, the Talmud and in ancient Greek medical literature. It dropped out of favor in the United States.

Initial fitting of the cap is slightly more involved than for a diaphragm, for example, and requires a trained health professional or physician.

Properly fitted thereafter by the user, the cap is regarded as more convenient because it may be left in several days, is less obtrusive than the diaphragm and does not interfere with erogenous areas.

The FDA panel, headed by Dr. Elizabeth Connell, obstetrician-gynecologist at the Emory University School of Medicine, officially recommended that the cap be removed after 48 hours. But many women's groups, who have been fitting and using it, have noted that some women have used it for a week or more at a time.

Yesterday's action culminates seven years of advocacy by women's health groups in an unusual partnership with a pharmaceutical house -- Lamberts.

About 50,000 women have participated in cervical-cap trials and another 2,000 in a three-year study comparing the cap and diaphragm. The latter was conducted by the National Institute of Child Health and Human Development at eight California clinics.

That study was headed by Dr. Gerald S. Bernstein, professor of obstetrics and gynecology at the University of Southern California.

He reported finding the cap comparable to the diaphragm in preventing pregnancy when used correctly. Normally, the device is filled with spermicidal cream or spermicidal gel and fitted tightly over the mouth of the cervix.

Cynthia A. Pearson is program director for the National Women's Health Network and the National Cervical Cap Advisory Committee, which have been coordinating the campaign for the cap's approval in the United States.

Pearson told the advisory panel that, although the cervical cap "isn't perfect, it compares well to the other contraceptive methods currently available to women and for some" is the best method.