The Food and Drug Administration said Tuesday that it would make the most widely known morning-after pill available without a prescription to girls and women ages 15 and older, and also make the pill available on drugstore shelves, instead of keeping it locked up behind pharmacy counters.

Until this decision the pill, Plan B One-Step, which is used after sexual intercourse to help prevent pregnancy, was available without a prescription only for ages 17 and older.

The decision did not address a federal judge’s ruling in early April that gave the drug agency 30 days to make the pill available for all ages without a prescription. In a scathing opinion handed down three weeks ago, Judge Edward R. Korman in the Eastern District of New York said the Obama administration had put politics before science in restricting access to the drug.

The F.D.A. and the White House said Tuesday that the Department of Justice was still deciding whether to appeal the ruling, something it can do independently of the drug agency’s decision on Tuesday.