WASHINGTON — An experimental COVID-19 drug that could soon become the first U.S.-authorized pill to treat the coronavirus faces one final hurdle Tuesday: A panel of government experts will scrutinize data on the medication from drugmaker Merck.

The Food and Drug Administration is asking its outside experts whether the agency should authorize the pill, weighing new information that it is less effective than first reported and may cause birth defects. The panel’s recommendations aren’t binding but often guide FDA decisions.

Tuesday’s meeting comes as U.S. infections are rising again and health authorities worldwide scramble to size up the threat posed by the new omicron variant.

If authorized, Merck’s pill would be the first that U.S. patients could take at home to ease symptoms and speed recovery, a major step toward reducing hospital case loads and deaths. The drug, molnupiravir, is already authorized for emergency use in the U.K.

Given the ongoing threat of the pandemic the FDA is widely expected to approve emergency use of Merck’s pill. But new data released last week paint a less compelling picture of the drug than when the Merck first publicized its early results in October.

On Friday, Merck said final study results showed molnupiravir reduced hospitalization and death by 30% among adults infected with the coronavirus, significantly lower than the 50% reduction it first announced based on incomplete results.

FDA regulators said they were still reviewing Merck’s update and would present a new assessment of the drug’s benefits to the outside panel. Molnupiravir’s effectiveness is a key question as panel members weigh whether to recommend the drug and for whom.

One key question is whether the drug should be restricted from use in pregnant women or women of child-bearing age.

In its safety review, FDA staffers said animal studies suggested Merck’s drug could cause birth defects when given at high doses. Regulators said they are considering a complete ban on molnupiravir’s use during pregnancy and other safeguards, including recommending contraceptives for some patients taking the pills.

Merck’s drug uses a novel approach to fight COVID-19: it inserts tiny errors into the coronavirus’ genetic code to stop the virus from reproducing. That genetic effect has raised concerns that the drug could cause mutations in human fetuses or even spur more virulent strains of the virus.

Another key question is whether the drug should be offered to patients who have been vaccinated or previously had COVID-19. Merck didn’t study the drug in vaccinated people, but data from a handful of patients with prior infections suggested it had little benefit. Still, it may be impractical for doctors to screen out those patients. The Merck drug works best when given within five days of first COVID-19 symptoms, underscoring the need for speedy treatment.

Merck tested the drug in adults with mild-to-moderate COVID-19 who were considered higher risk due to health problems like obesity, diabetes or heart disease. That’s the same group that currently receives antibody drugs, which help the immune system fight the virus. The FDA has authorized three antibody drugs for COVID-19 but all have to given by IV or injection at hospitals or clinics.

Merck was the first company to submit its COVID-19 pill to the FDA, but a rival drug from Pfizer is close behind and is also under review.

Pfizer’s drug is part of a decades-old family of antiviral pills known as protease inhibitors, a standard treatment for HIV and hepatitis C. They work differently than Merck’s pill and haven’t been linked to the kind of mutation concerns raised with Merck’s drug.