(Reuters) – Planned Parenthood and the American Civil Liberties Union’s Iowa branch said they sued on Tuesday to stop a state law that would impose the strictest abortion limits in the United States from taking effect.

Iowa’s Republican-controlled legislature voted last month to outlaw abortion after a fetal heartbeat is detected, effectively banning the procedure at about the six-week mark, which may be before a woman realizes she is pregnant.

The lawsuit was anticipated by some sponsors of the law, who hoped to trigger a challenge to Roe v. Wade, the U.S. Supreme Court’s 1973 decision that established that women have a constitutional right to an abortion.

The lawsuit in Polk County District Court in Des Moines, the state capital, seeks a hearing within two weeks to block the law from going into effect on July 1.

“Iowa will not go back in time by taking away this right,” Suzanna de Baca, the president of Planned Parenthood of the Heartland, said at a news conference. “Planned Parenthood is challenging this law because the Iowa Constitution is clear a woman has a right to access a safe and legal abortion.”

There are some exceptions to the ban, including some cases of rape and incest and serious medical emergencies, but Planned Parenthood, whose services include abortions, and ACLU say the exceptions are too narrow.

Abortion opponents hope such a lawsuit could bring the divisive abortion issue back before the U.S. Supreme Court in the belief that the 5-4 conservative majority could curtail abortion access or ban it outright.

Iowa Governor Kim Reynolds, a Republican, anticipated the legal challenge, a spokeswoman said.

“We knew there would be a legal fight, but it’s worth having to protect innocent life,” Brenna Smith said in an email.

Republican state Senator Rick Bertrand said last month the law was in part “an opportunity to take a run at Roe v. Wade.”

Planned Parenthood and the ACLU said they hope to avoid that possibility by only challenging the law under the Iowa Constitution. They say the state constitution, not the U.S. Constitution, guarantees a woman’s right to abortion.

A 2017 Iowa law that requires a minimum 72-hour waiting period before obtaining an abortion is currently blocked while the Iowa Supreme Court decides whether to strike it down.

Iowa Attorney General Tom Miller, a Democrat, said he would not defend the abortion ban because he believes it would undermine the rights of women, according to a letter from his office to Reynolds and four cabinet members.

The ban will, if the state executive council approves, be defended by the Thomas More Society, an anti-abortion legal group, the letter said.

(Reporting by Jonathan Allen in New York and Bernie Woodall in Fort Lauderdale, Florida; editing by Scott Malone and Tom Brown)