WASHINGTON >> In a surprise move, the nation’s health secretary stopped the Plan B morning-after pill from moving onto drugstore shelves next to the condoms, deciding Wednesday that young girls shouldn’t be able to buy it on their own.

The Food and Drug Administration was preparing to lift a controversial age limit and make Plan B One-Step the nation’s first over-the-counter emergency contraceptive, available for purchase by people of any age without a prescription.

But Health and Human Services Secretary Kathleen Sebelius intervened at the eleventh hour and overruled her own experts.

Plan B instead will remain behind the pharmacy counter, as it is sold today — available without a prescription only for those 17 and older who show an ID proving their age.

Sebelius’ reason: Some girls as young as 11 are physically capable of bearing children, and Plan B’s maker didn’t prove that younger girls could properly understand how to use this product without guidance from an adult.

"It is common knowledge that there are significant cognitive and behavioral differences between older adolescent girls and the youngest girls of reproductive age," Sebelius said in a statement. "I do not believe enough data were presented to support the application to make Plan B One-Step available over-the-counter for all girls of reproductive age."

It was the latest twist in a nearly decade-long push for over-the-counter sales of pills that can prevent pregnancy if taken soon enough after unprotected sex. Major doctors’ groups and women’s health advocates say easier, quicker access to those pills could cut the nation’s high number of unplanned pregnancies.

The decision shocked maker Teva Pharmaceuticals, which had been gearing up for over-the-counter sales to begin by month’s end, and women’s health groups.

"We are outraged that this administration has let politics trump science," said Kirsten Moore of the Reproductive Health Technologies Project, an advocacy group. "There is no rationale for this move."

"What else can this be but politics?" said Cynthia Pearson, executive director of the National Women’s Health Network, an advocacy group that supports making Plan B available to all ages. "It’s not science. It’s not medicine. It’s not women’s health."

Indeed, FDA Commissioner Dr. Margaret Hamburg made clear in her own statement that the decision is highly unusual. She said her agency’s drug-safety experts had carefully considered the question of young girls and that she had agreed that Plan B’s age limit should be lifted.

"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 use for all females of child-bearing potential," Hamburg wrote.

But, she added, she had followed her boss’ order to deny Teva’s application.

"We commend the FDA for making the recommendation … and we are disappointed that at this late date, the Department of Health and Human Services has come to a different conclusion," said a statement Teva issued Wednesday.

The company said it would review the decision before determining next steps.

Already, the FDA’s age limits have gone to court. In 2009, a federal judge said the agency had set them initially based on politics, not science, and ordered the agency to reconsider. A hearing already was scheduled for next week to consider whether the FDA should be held in contempt of court for not doing so earlier.