The reversal by the government means that any woman or girl will soon be able to walk into a drugstore and buy the pill, Plan B One-Step, without a prescription.

The Justice Department had been fighting to prevent that outcome, but said late Monday afternoon that it would drop its appeal of a judge’s order to make the drug more widely available. In a letter to Judge Edward R. Korman of the United States District Court for the Eastern District of New York, the administration said it would comply with his demands that the Food and Drug Administration be allowed to certify the drug for nonprescription use.

The Justice Department appears to have concluded that it might lose its case with the appeals court and would have to decide whether to appeal to the Supreme Court. That would drastically elevate the debate over the politically delicate issue for Mr. Obama.