In a highly unusual move, the head of the U.S. Department of Health and Human Services on Wednesday decided that the morning-after emergency contraceptive Plan B One-Step may not be sold without a prescription for women of all ages, even though the Food and Drug Administration was poised to approve over-the-counter sales.

The eleventh-hour move by Secretary Kathleen Sebelius was reminiscent of the political wrangling that prevented easier access to Plan B under the Bush administration. In 2006 - three years after the manufacturer asked for over-the-counter status - the FDA said only women over 17 could get it without a prescription.

"I'm feeling completely outraged and betrayed," said Princeton University population researcher James Trussell, who has worked since 1992 to make emergency contraception widely and readily available. "I don't know which is worse, what the Bush administration did or what this administration did. But it's still politics trumping science."

FDA commissioner Margaret Hamburg issued a statement Wednesday that she agreed with FDA experts who reviewed all the studies and recommended over-the-counter status.

"There is adequate and reasonable, well-supported, and science-based evidence that Plan B One-Step is safe and effective and should be approved for nonprescription used for all females of child-bearing" age.

In overruling the FDA, HHS Secretary Kathleen Sebelius drew exactly the opposite conclusion.

"Because I do not believe enough data were presented to support the application to make Plan B One-Step available over the counter...I have directed the FDA to issue a ...letter denying" the request.

Israel-based Teva Pharmaceuticals, which has its American headquarters in North Wales, Pa., markets the oral contraceptive, which contains the hormone progestin and can be taken up to 72 hours after sex to prevent pregnancy. "We commend the FDA for making the recommendation to approve providing women with increased over-the-counter access to Plan B One-Step and we are disappointed that at this late date, the Department of Health and Human Services has come to a different conclusion," a company statement said.

The drug will remain on the market, but women under the age of 17 must have a prescription.