WASHINGTON — President Obama, who took office pledging to put science ahead of politics, averted a skirmish with conservatives in the nation’s culture wars on Thursday by endorsing his health secretary’s decision to block over-the-counter sales of an after-sex contraceptive pill to girls under age 17.

The administration action inevitably raised questions about whether politics was trump in this instance — especially from disappointed supporters in the scientific and women’s rights communities. Mr. Obama, who had criticized how his predecessor made decisions on issues like contraceptives, sought to dispel that idea in remarks to White House reporters.

“I did not get involved in the process,” he quickly asserted.

Mr. Obama said the decision was made by his secretary of health and human services, Kathleen Sebelius. On Wednesday, in a rare move, she overruled the Food and Drug Administration, which had recommended that the morning-after pill Plan B One-Step is safe and should be sold without a prescription to people under 17, just as it is now to those who are 17 and older.

“I will say this, as the father of two daughters: I think it is important for us to make sure that we apply some common sense to various rules when it comes to over-the-counter medicine,” Mr. Obama said.