The U.S. Supreme Court on Friday appeared skeptical of President Biden’s broad vaccination-or-testing requirement for the nation’s large employers, reports The Washington Post, thus “casting doubt” on the president’s “most ambitious plan to fight the pandemic.” The justices did, however, seem more likely to back to a separate requirement that “health care workers at facilities that receive federal money be vaccinated,” adds The New York Times.

The latter regulation was the subject of the second argument heard by the court on Friday.

The justices’ decision on both matters could come quickly, considering they are mulling over “emergency petitions to either allow the regulations to go into effect or stop them,” per the Post.

When it came to the large employer mandate, the court’s conservative majority was more inclined to believe states or Congress should regulate such decisions rather than the federal govenment, per the Times. They were also concerned Biden’s requirement was too broad; for instance, Chief Justice John Roberts and Justice Amy Coney Barrett asked if OSHA could have instead drafted a “more targeted” initiative based on workplace conditions, per the Post.

The three liberal justices, however, “expressed disbelief” that anyone would try to block Biden’s policy while “the pandemic continues to rage,” writes the Post.

“We know the best way to prevent spread is for people to get vaccinated,” said Justice Elena Kagan. “This is the policy that is most geared to stopping all this.”

The administration’s rule, which was supposed to go into effect on Jan. 4, mandates employers with over 100 employees to require vaccination or weekly testing as a condition of employment. OSHA pushed back the date in response to legal challenges.

Regarding a separate policy for health-care workers, justices felt that “in keeping with other kinds of federal oversight,” as well as broadly supported by the medical community, per the Times.