A federal appeals court upheld key parts of Texas's strict anti-abortion law on Tuesday, a decision that could leave as few as seven abortion clinics in the nation's second largest state.

The decision by the 5th U.S. Circuit Court of Appeals upholds requirements that abortion clinics meet hospital-level operating standards, which owners of small clinics say demand millions of dollars in upgrades they can't afford and will leave many women hundreds of miles away from an abortion provider. But the court said abortion clinics failed to prove that the restrictions would unduly burden a "large fraction" of women.

Republican Gov. Greg Abbott and other conservatives say the standards protect women's health. But abortion-rights supports say the law is a thinly veiled attempt to block access to abortions in Texas, and they promised to appeal to the U.S. Supreme Court, which temporarily sidelined the law last year.

"Not since before Roe v. Wade has a law or court decision had the potential to devastate access to reproductive health care on such a sweeping scale," said Nancy Northrop, president and CEO of the Center for Reproductive Rights.

Texas will be able to start enforcing the restrictions in about three weeks unless the Supreme Court steps in and temporarily halts the decision, said Stephanie Toti, an attorney for the center. Only seven abortion facilities in Texas, including four operated by Planned Parenthood, meet the more robust requirements.

The ruling, made by a three-judge panel, is the 5th Circuit's latest decision in a lawsuit challenging some of the toughest abortion restrictions in the country.

The New Orleans-based court — considered one of the most conservative in the nation — allowed Texas to enforce the restrictions when abortion providers first sued in 2013, but the U.S. Supreme Court put the law on hold last year and ordered the 5th Circuit to reconsider.

Texas currently has about 17 abortion providers, down from 40 clinics in 2012. That sharp decline began after the 5th Circuit upheld another part of the 2013 law that required doctors to have admitting privileges at nearby hospitals.

Republican Texas Attorney General Ken Paxton, a strong supporter of the law, praised the court's latest ruling.

"Abortion practitioners should have no right to operate their businesses from sub-standard facilities and with doctors who lack admitting privileges at a hospital," Paxton said.

Under the new restrictions, the only remaining abortion facilities in Texas would be in major cities. One exception would be in McAllen, near the Texas-Mexico border, which the 5th Circuit exempted from some restrictions — but Toti said even those exemptions are so limited that it may not be practical to keep that McAllen clinic open.

But for women in El Paso, the closest abortion provider in Texas would require a 1,200-mile round trip to San Antonio, or they would have to cross the border into New Mexico.

The appeals court found that option suitable, noting that a clinic was just across the border in Santa Teresa, New Mexico. The court also said abortion clinics failed to show that most women would be unconstitutionally burdened by the law.

"Although the nearest abortion facility in Texas is 550 miles away from El Paso, there is evidence that women in El Paso can travel the short distance to Santa Teresa to obtain an abortion and, indeed, the evidence is that many did just that," the court wrote in a 56-page opinion.

Attorneys for the state dismissed opponents' arguments about women being burdened by fewer abortion facilities, saying that nearly 9 in 10 women in Texas would still live within 150 miles of a provider.

A new slate of conservative leaders in Texas has vowed to continue stifling abortion-rights efforts. George P. Bush, the son of expected 2016 presidential hopeful Jeb Bush and nephew of former President George W. Bush, made an anti-abortion rally at the Capitol his first public event since being sworn in as land commissioner, along with Abbott's wife, Cecilia.

