Texas woke up to the strictest anti-abortion law in the country after the US Supreme Court declined to act on a request by abortion-rights groups to block the law banning the procedure after six weeks of pregnancy.

It was a victory for conservatives, who have long sought to eliminate abortion access in the United States.

Prominent Democrats including President Joe Biden voiced outrage, saying the Texas law that came into effect at midnight on Tuesday (local time) violated the right to abortion access established by the Supreme Court’s landmark decision in Roe v Wade in 1973.

“My administration … will protect and defend that right,” Mr Biden said.

Abortion rights activists said such a ban has not been enacted in any US state since that landmark ruling.

Texas abortion providers worked until almost the midnight deadline, when the 6-3 conservative-majority court’s inaction allowed the law to be enforced while abortion-rights groups further pursue their legal challenge to its constitutionality.

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The justices could yet take action on the Texas case. But they have already agreed to hear arguments in Mississippi’s effort to overturn Roe v Wade.

The law amounts to a near-total ban on abortion procedures given that 85 per cent to 90 per cent of abortions occur after six weeks of pregnancy, and would likely force many clinics to close, the abortion-rights groups said.

A majority of Americans believe abortion should be legal in the United States, according to Reuters/Ipsos polling. Some 52 per cent said it should be legal in most or all cases, with just 36 per cent saying it should be illegal in most or all cases.

But it remains a deeply polarising issue, with a majority of Democrats supporting abortion rights and a majority of Republicans opposing them.