The Supreme Court has decided to keep women's access to a widely used abortion pill while a legal challenge to its Food and Drug Administration approval goes on.
The justices weighed up arguments over whether restrictions from lower-court rulings would severely disrupt the availability of the drug, mifepristone, which is the most common abortion method in the US.
It has repeatedly been found to be safe and effective, and has been used by more than 5 million women in the US since the FDA approved it in 2000.
The Supreme Court had initially said it would decide by Wednesday whether the restrictions could take effect while the case continues.
A one-sentence order signed by Justice Samuel Alito on Wednesday gave the justices two additional days until Friday night to make a decision, without explanation.
The challenge to mifepristone, brought by anti-abortion campaigners, is the first abortion controversy to reach the nation's highest court since its conservative majority overturned Roe v Wade 10 months ago and allowed more than a dozen states to effectively ban abortion outright.
In his majority opinion, Justice Alito said one reason for overturning Roe was to remove federal courts from the abortion fight.
"It is time to heed the Constitution and return the issue of abortion to the people's elected representatives," he wrote.
But even with their court victory, abortion opponents returned to federal court with a new target - medication abortions, which make up more than half of all abortions in the United States.
Women seeking to end their pregnancies in the first 10 weeks without more invasive surgical abortion can take mifepristone, along with misoprostol.
The FDA has eased the terms of mifepristone's use over the years, including allowing it to be sent through the mail in states that allow access.
The abortion opponents filed suit in Texas in November, asserting that FDA's original approval of mifepristone 23 years ago and subsequent changes were flawed.
They won a ruling on April 7 by US District Judge Matthew Kacsmaryk, an appointee of former President Donald Trump, revoking FDA approval of mifepristone. The judge gave the Biden administration and New York-based Danco Laboratories, mifepristone's maker, a week to appeal and seek to keep his ruling on hold.
Responding to a quick appeal, two more Trump appointees on the 5th US Circuit Court of Appeals said the FDA's original approval would stand for now.
But Judges Andrew Oldham and Kurt Englehardt said most of the rest of Judge Kacsmaryk's ruling could take effect while the case winds through federal courts.
Their ruling would effectively nullify changes made by the FDA starting in 2016, including extending from seven to 10 weeks of pregnancy when mifepristone can be safely used.
The court also said that the drug can't be mailed or dispensed as a generic and that patients who seek it need to make three in-person visits with a doctor. Women also might be required to take a higher dosage of the drug than the FDA says is necessary.
The administration and Danco Laboratories have said that if restrictions take effect while the case proceeds, it will be chaos.
Potentially adding to the confusion, a federal judge in Washington has ordered the FDA to preserve access to mifepristone under the current rules in 17 Democratic-led states and the District of Columbia that filed a separate lawsuit.
The Biden administration has said the rulings conflict and create an untenable situation for the FDA.
