By Andrew Chung

(Reuters) – Abortion rights groups filed an emergency request at the U.S. Supreme Court on Monday to block a Texas law banning abortion after six weeks of pregnancy, which is set to take effect on Wednesday.

The groups, including Planned Parenthood and other abortion and women’s health providers, told the court that the law would “immediately and catastrophically reduce abortion access in Texas, barring care for at least 85% of Texas abortion patients” and would likely force many abortion clinics to close.

The groups challenged the law in federal court in Austin in July, contending it violates a woman’s constitutional right to an abortion.

The law, signed on May 19, is unusual in that it gives private citizens the power to enforce it by enabling them to sue anyone who assists a woman in getting an abortion past the six-week cutoff.

The law is among of a number of “heartbeat” abortion bans enacted in Republican-led states. These laws seek to ban the procedure once the rhythmic contracting of fetal cardiac tissue can be detected, often at six weeks – sometimes before a woman realizes she is pregnant.

Courts have blocked such bans as a violation of Roe v. Wade, the landmark 1973 Supreme Court ruling that legalized abortion nationwide.

The state of Mississippi has asked the Supreme Court to overturn Roe v. Wade in a major case the justices agreed to hear over a 2018 law banning abortion after 15 weeks. The justices will hear arguments in their term that begins in October, with a ruling due by the end of June 2022.

The Texas lawsuit seeks to prevent judges, county clerks and other state entities from enforcing the law through citizen lawsuits. The plaintiffs also sued the director of an anti-abortion group that they said has threatened enforcement actions under the new law.

A federal judge rejected a bid to dismiss the case, prompting an immediate appeal to the New Orleans, Louisiana-based 5th U.S. Circuit Court of Appeals, which halted further proceedings in the case. On Sunday, the 5th Circuit denied a request by the abortion providers to block the law pending the appeal.

The plaintiffs on Monday asked the Supreme Court to block the Texas law or allow proceedings in the lower court to continue.

(Reporting by Andrew Chung in New York, additional reporting by Gabriella Borter; Editing by Scott Malone and Jonathan Oatis)