WASHINGTON (AP) — The U.S. Supreme Court on Tuesday blocked key parts of a 2013 law in Texas that had closed all but eight facilities providing abortions in America's second most-populous state.

In an unsigned order, the justices sided with abortion rights advocates and health care providers in suspending an Oct. 2 ruling by a panel of the New Orleans-based U.S. 5th Circuit Court of Appeals that Texas could immediately apply a rule making abortion clinics statewide spend millions of dollars on hospital-level upgrades.

The court also put on hold a provision of the law only as it applies to clinics in McAllen and El Paso that requires doctors at the facilities to have admitting privileges at nearby hospitals. The admitting privileges rule remains in effect elsewhere in Texas.

Justices Samuel Alito, Antonin Scalia and Clarence Thomas said they would have ruled against the clinics in all respects.

The 5th Circuit is still considering the overall constitutionality of the sweeping measure overwhelmingly passed by the GOP-controlled Texas Legislature and signed into law by Gov. Rick Perry last year.

Even as it weighs the merits of the law, the appeals court had said it could be enforced — opening the door for the emergency appeal to the Supreme Court.

"We're seeing the terrible impact these restrictions have on thousands of Texas women who effectively no longer have access to safe and legal abortion," said Cecile Richards, president of Planned Parenthood Federation of America. "We're relieved that the court stepped in to stop this, and we hope this dangerous law is ultimately overturned completely."

Abortion opponents predicted they will ultimately prevail.

"This does not protect the health and safety of women who are undergoing abortion," said Joe Pojman, executive director of Texas Alliance for Life. ""This is definitely a short-term loss, but not necessarily a long- term loss."

The 5th Circuit decision had blocked an August ruling by Austin-based U.S. District Judge Lee Yeakel, who had found that requiring hospital-style upgrades was less about safety than making access to abortion difficult. Yeakel's ruling temporarily suspended the upgrade rules before they could go into effect Sept. 1 — and the order from the Supreme Court means they are on hold again.

Allowing the rules on hospital-level upgrades to be enforced — including mandatory operating rooms and air filtration systems — shuttered more than a dozen clinics across Texas.

Until the nation's highest court intervened, only abortion facilities in the Houston, Austin, San Antonio and the Dallas-Fort Worth areas remained open. And none was left along the Texas-Mexico border or outside any of the state's largest urban areas.

Some other clinics had closed even earlier amid enforcement of the rule on admitting privileges at nearby hospitals. That portion has already been upheld twice by the appeals court.

The fight over the Texas law is the latest over tough new abortion restrictions that have been enacted across the country. The office of Texas Attorney General Greg Abbott, a Republican who is the favorite in next month's governor's race, is leading the defense of the law.

Democrat Wendy Davis launched her campaign for governor behind the celebrity she achieved through a nearly 13-hour filibuster last summer that temporarily blocked the law's passage. Davis said she was "thankful that women can continue to make their own personal decisions." Abbott's office said he would continue to defend the law.

Attorneys for the state have denied that Texas women would be burdened by fewer abortion facilities, saying nearly 9 in 10 would still live within 150 miles of a provider. The law's opponents note that leaves nearly a million Texas women embarking on drives longer than three hours to get an abortion.

Hilltop Women's Reproductive Services in El Paso has been referring women who want abortions to another clinic it owns in New Mexico. Gloria Martinez, Hilltop's administrative nurse, said she would call state officials Wednesday before deciding whether the clinic will resume performing abortions.

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Associated Press writers Jim Vertuno and Will Weissert in Austin, Texas, and Juan Carlos Llorca in El Paso contributed to this report.