The Obama administration on Monday urged the U.S. Supreme Court to strike down a Texas abortion law that has shuttered nearly half the clinics in the state, saying the Republican-backed regulations would harm rather than protect women's health.

Intervening in the Supreme Court's first abortion case since 2007, the administration said the new Texas rules for clinics and physicians who perform abortions are far more restrictive than other regulations upheld by the justices over the years.

If allowed to take full effect, U.S. Solicitor General Donald Verrilli wrote, the law would close many more of the state's clinics and force hundreds of thousands of Texas women to travel great distances if they seek to terminate pregnancies.

"Those requirements are unnecessary to protect - indeed, would harm - women's health, and they would result in closure of three quarters of the abortion clinics in the state," Verrilli wrote.

The administration's "friend of the court" brief siding with the clinics challenging the law comes in one of the most politically charged disputes this presidential election year.

The case does not test the fundamental right to abortion established by the court's 1973 Roe v. Wade decision, but could impact women's access to abortion services nationwide. Depending on how the justices rule, they could encourage, or dissuade, other states to impose regulations.

In the past, Republican administrations have sided with states trying to restrict abortions while Democrats have joined physicians and clinics opposed to the regulations.

The Obama administration did not fully embrace the clinic challengers' position, however.

The clinics that sued Texas, represented by the New York-based Center for Reproductive Rights (CRR), say judges trying to determine whether a regulation unconstitutionally burdens a woman's right to abortion should look at legislators' purpose or motives.

In this case, CRR lawyers said, the state's assertions of health concerns "are nothing more than a pretext for restricting access to abortion."

Administration lawyers emphasized a judicial review tied to the effects of a law. That more nuanced stance might have been crafted to appeal to pivotal justice Anthony Kennedy, who in past cases has backed a fundamental right to abortion but has broken from his abortion-rights colleagues to endorse certain regulations.

Obama administration lawyers said the law's requirements that clinics have hospital-grade facilities and clinic doctors obtain admitting privileges at a local hospital were unnecessary because abortions provided in Texas are safe and have produced a low rate of complications.

Briefs from state officials and from their supporters in the case are due in the coming weeks. Texas officials have argued in previous filings that U.S. states have an interest in protecting thehealth of a woman seeking an abortion and urged courts to defer to legislative authority.