The Supreme Court on Friday retained full access for now to a key drug that has been taken by millions of women to terminate early pregnancies, its first major abortion-related decision since overturning Roe v. Wade's constitutional guarantee of abortion rights last year.

The court put on hold a lower court's ruling in favor of antiabortion groups, which said the Food and Drug Administration was wrong to make the drug mifepristone more widely available. A legal battle over whether to permanently reimpose restrictions, and whether the FDA had properly approved use of the drug more than 20 years ago, will continue.

As is typical in emergency actions, the majority did not explain its reasoning for putting the lower court decision on hold. In the only noted dissents, Justices Clarence Thomas and Samuel A. Alito Jr. said they would not have granted the Biden administration's request for a stay of the lower court decision. Thomas did not explain his reasoning. Alito said the administration and the public would not have been harmed by agreeing with the lower court to roll back restrictions loosened by the FDA in recent years.

"It would simply restore the circumstances that existed (and that the Government defended) from 2000 to 2016 under three Presidential administrations," Alito wrote. He disputed that the court's intervention at this time would have sent a signal.

"Contrary to the impression that may be held by many, that disposition would not express any view on the merits of the question whether the FDA acted lawfully in any of its actions regarding mifepristone," Alito wrote.

President Joe Biden quickly praised the court's action. "As a result of the Supreme Court's stay, mifepristone remains available and approved for safe and effective use while we continue this fight in the courts. I continue to stand by FDA's evidence-based approval of mifepristone," the president said in a statement.

"The stakes could not be higher for women across America. I will continue to fight politically-driven attacks on women's health. But let's be clear - the American people must continue to use their vote as their voice, and elect a Congress who will pass a law restoring the protections of Roe v Wade."

The court's order on Friday was the latest development in what has been a rapid and at times confusing legal battle over mifepristone, which is used as part of a two-drug regimen in more than half of the nation's abortion procedures. The second drug, misoprostol, can also be used on its own to terminate early pregnancies, usually with more cramping and bleeding.

Abortion medications have increased in importance as states limit or ban abortions after the Supreme Court's ruling last June in Dobbs v. Jackson Women's Health Organization, in part because they can be sent by mail and taken at home.

Antiabortion groups have attacked the FDA's approval of mifepristone, as well as more recent changes making the drug more accessible. Drugmakers, the Biden administration and abortion providers say all the agency's decisions are science based and proper, based on two decades of accumulated clinical studies of the drug's use.

The justices are considering a decision of the U.S. Court of Appeals for the 5th Circuit that rolled back the FDA's actions since 2016 increasing access to mifepristone - approving the drug's use through 10 weeks of pregnancy instead of seven, allowing patients to get mifepristone through the mail and authorizing prescriptions by medical professionals other than doctors.

The appeals court action followed U.S. District Judge Matthew Kacsmaryk's recent ruling in Texas to suspend the FDA's approval of mifepristone altogether. More than 5 million women have used mifepristone to end their pregnancies since it was first cleared for use in the United States in 2000.

The Biden administration and drugmakers called Kacsmaryk's decision an unprecedented attack on the expertise of the FDA, which relied on data from dozens of clinical trials when it approved the drug. They told the Supreme Court the lower court rulings would create chaos for abortion providers and upend the FDA's regulatory authority, with far-reaching repercussions for other drugs.

The challengers, an association of antiabortion doctors and others, said the FDA had succumbed to political pressure in approving the drug and then lifting restrictions over its use.

"For nearly a quarter-century," the antiabortion doctors said in their filing to the Supreme Court, the FDA and the manufacturer of mifepristone "have brazenly flouted the law and applicable regulations, disregarded holes and red flags in their own safety data, intentionally evaded judicial review, and continually placed politics above women's health."

The group behind the Texas lawsuit, the Alliance for Hippocratic Medicine, filed its challenge in Amarillo, where Kacsmaryk - a nominee of President Donald Trump with long-held antiabortion views - is the sole sitting judge. The group has a mailing address in Tennessee, records show, and incorporated in Texas several months before submitting its legal challenge.

Kacsmaryk agreed with the alliance's claim that the FDA did not follow proper procedure or sufficiently consider safety concerns. The judge's April 7 ruling was the first time a court issued an order to suspend a long-approved medication, and medical experts said the decision ignored hundreds of scientific studies attesting to the drug's safety.

Language in Kacsmaryk's ruling echoed terminology used by antiabortion activists, referring to abortion providers as "abortionists" and to fetuses and embryos as "unborn humans."

The Justice Department and Danco Laboratories, the pharmaceutical company that makes mifepristone, appealed the ruling to the 5th Circuit.

The appeals court agreed with Kacsmaryk that the FDA failed to examine relevant data when it eliminated certain safeguards in 2016. The 5th Circuit also said the individual doctors and antiabortion associations probably have sufficient legal grounds to proceed with their challenge because there are instances when a medication abortion is unsuccessful and requires additional treatment.

The appeals court scheduled oral argument for May 17.

Solicitor General Elizabeth B. Prelogar said in a brief to the Supreme Court that challengers should not be granted legal standing because they do not take or prescribe mifepristone. The challengers, she wrote, were ignoring the significant chaos a ruling in their favor would cause for patients, prescribers and the health-care system.

"Nor do they justify the harm of denying women lawful access to a drug under conditions FDA determined are safe and effective and instead requiring them to undergo invasive surgical procedures," Prelogar wrote

Adding to the complex legal situation, on the same day that Kacsmaryk ruled, a federal judge in Washington state issued a contradictory decision in a separate mifepristone-related lawsuit filed by Democratic attorneys general. The judge ordered the FDA not to make any changes to the availability of the drug in 17 states and the District of Columbia, all of which are part of the litigation.

The cases before the Supreme Court are FDA v. Alliance for Hippocratic Medicine and Danco Laboratories v. Alliance for Hippocratic Medicine.