WASHINGTON — The Supreme Court is expected on Wednesday to decide the fate of a crucial abortion pill that is used in more than half of abortions across the United States while an appeal moves forward.

The court is weighing an emergency application by the Biden administration to maintain the Food and Drug Administration’s approval of the drug after an appeals court said it would place limitations on the medication, mifepristone.

Justice Samuel A. Alito Jr. had issued a stay in the case that is set to expire at midnight, meaning the court is likely to act before then, although it could extend the deadline or fail to act.

The prolonged legal clash reflects a muddled and fast-moving landscape for mifepristone, marked by conflicting Federal District Court decisions and an appeals panel ruling that further complicated the drug’s status.

After the Supreme Court overturned the constitutional right to an abortion last summer, political and legal battles have centered on medications used for the procedure. In some conservative states, lawmakers have targeted abortion pills.

Mifepristone is typically used in combination with a second drug, misoprostol, in the first 10 weeks of pregnancy. The first drug used in the regimen blocks progesterone, a hormone that allows a pregnancy to develop, and the second, taken one or two days later, prompts contractions and helps the uterus expel its contents.

The dispute started in Texas in November, when an umbrella group of anti-abortion medical organizations and several doctors sued the Food and Drug Administration, challenging its approval more than two decades ago of the abortion pill.

In their suit, the anti-abortion groups claimed that the F.D.A. did not follow proper protocols when it approved the drug in 2000. The groups said that the agency had also ignored dangers of the drug in the years since.

The F.D.A., countering the plaintiffs’ claims, has said that the drug was properly approved more than 20 years ago and that it is safe.

The lawsuit was filed in the Amarillo division of the U.S. District Court of the Northern District of Texas, where a single federal judge, Matthew J. Kacsmaryk, an appointee of President Donald J. Trump, hears cases.

Judge Kacsmaryk, a longtime opponent of abortion, is a former lawyer for First Liberty Institute, a legal group focused on religious liberty cases that has long backed conservative causes.

This month, Judge Kacsmaryk announced a preliminary ruling that invalidated the F.D.A.’s approval of the drug. But the judge said that the agency had a week to seek emergency relief before his ruling would take effect.

Judge Kacsmaryk suffused his ruling with the language of the anti-abortion movement, referring to abortion providers as “abortionists” and a fetus or embryo as an “unborn human” or “unborn child.” He appeared to agree with virtually all of the claims made by the anti-abortion groups.

Less than an hour later, another federal judge, Thomas O. Rice, who was appointed by President Barack Obama, issued a contradictory ruling in Washington State in a different lawsuit. Judge Rice blocked the F.D.A. from limiting the availability of mifepristone in much of the country.

The Washington State lawsuit, filed by Democratic attorneys general in 17 states and the District of Columbia, is a direct challenge to the Texas case.

The Biden administration immediately appealed the ruling by the federal judge in Texas, and a divided three-judge panel of the U.S. Court of Appeals for the Fifth Circuit, based in New Orleans, announced that mifepristone could remain legal and available while the lawsuit makes its way through the courts.

The panel rejected Judge Kacsmaryk’s finding that the F.D.A.’s approval of mifepristone more than 20 years ago was not valid. At the same time, the judges blocked more recent steps by the F.D.A. to make the drug more easily available, including permissions to send the pills by mail. Experts said the consequences could be far-reaching, creating more obstacles for a patient’s ability to secure the drug.

The next day, Judge Rice reaffirmed his ruling, ordering the F.D.A. to maintain the status quo in the 18 jurisdictions, sowing further confusion about the availability of the abortion pill.

The dueling orders all but guaranteed that the case would go to the Supreme Court.

The Biden administration, seeking emergency relief, asked the justices to pause the appeals court ruling that sought to limit access to the pill. In its brief, the government argued that the decision had sweeping consequences, not only for abortion pill access but also for the broader pharmaceutical industry.

“If allowed to take effect, the lower courts’ orders would upend the regulatory regime for mifepristone, with sweeping consequences for the pharmaceutical industry, women who need access to the drug and F.D.A.’s ability to implement its statutory authority,” the brief said.