The US Supreme Court ruled on Thursday to permit, for now, abortions to be performed in Idaho when pregnant women are facing medical emergencies, as the justices dispensed with the contentious issue without actually deciding the case on its merits.

The 6-3 ruling, with three of the six conservative justices dissenting, effectively reinstated a lower court's decision that Idaho's Republican-backed near-total abortion ban must yield to a 1986 US law known as the Emergency Medical Treatment and Labor Act (EMTALA) when the two statutes conflict.

A version of the ruling was inadvertently posted to the court's website on Wednesday in the second instance in the past two years of the disclosure of a major abortion decision before its formal issuance.

US President Joe Biden's administration had sued Idaho, arguing that EMTALA takes precedence over state law. EMTALA ensures that patients can receive emergency care at hospitals that receive funding under the federal Medicare programme. Idaho is among six states with abortion bans that offer no exceptions to protect the health of pregnant women.

The court's decision, an unsigned, one-line order, lifted a block, or stay, that the justices had placed on the lower court's ruling in January. But the Supreme Court did not resolve the underlying legal dispute, opting instead to dismiss the case as "improvidently granted".

Liberal Justice Ketanji Brown Jackson in a separate opinion agreed with the court's decision to lift its stay, but said she would not have dismissed the case, calling the legal situation a "fragile detente".

"This court had a chance to bring clarity and certainty to this tragic situation, and we have squandered it," Jackson wrote. "And for as long as we refuse to declare what the law requires, pregnant patients in Idaho, Texas and elsewhere will be paying the price."

In May 2022, a draft of the Supreme Court's landmark ruling rolling back abortion rights was leaked to the news media a month before the decision was formally issued. The Supreme Court carried out an investigation but failed to identify the leaker. The ruling overturned the 1973 Roe v Wade precedent that had recognised a constitutional right to abortion and legalised the procedure nationwide.

Following the 2022 abortion ruling, a series of states, including Idaho, enacted Republican-backed laws imposing bans on abortion. (Reuters)