Danny Johnston / AP

Arkansas Gov. Mike Beebe talks to reporters Monday, March 4, at the state Capitol in Little Rock after vetoing legislation that would have banned abortions 12 weeks into a pregnancy.

Arkansas Gov. Mike Beebe vetoed a controversial bill Monday that would have made abortions illegal after only 12 weeks, calling it "blatantly unconstitutional."

Arkansas already has one of the most restrictive abortion laws in the U.S. after the Republican-led Legislature last week overrode Beebe's veto of a similar bill that set the legal abortion threshold at 20 weeks' gestation. Most states allow abortions until the 22nd to 24th week.

That law took effect immediately. The new measure, which would be the most restrictive in the nation if the Legislature overrides Beebe's veto, wouldn't take effect until 90 days after the Legislature adjourns later this month or in early April.

The measure includes exceptions for rape and incest, medical conditions that would not allow the fetus to live long after birth, and circumstances under which delivery would significantly threaten the life of the woman.

Lawmakers need only a simple majority to override the veto.

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In a statement, Beebe, a Democrat, said the 12-week law "blatantly contradicts the United States Constitution, as interpreted by the Supreme Court."

The American Civil Liberties Union of Arkansas has already said it would sue if the law goes into effect.

Beebe noted that "outside groups" had offered to represent the state in any litigation, but he said that would "only lessen the state's own litigation costs," not eliminate them.

"Lawsuits challenging unconstitutional laws also result in the losing party — in this case, the state — being ordered to pay the costs and attorneys' fees incurred by the litigants who successfully challenge the law," he said.

Related: 40 years after Roe v. Wade, more states restricting abortion

The measure, introduced by Sen. Jason Rapert, a Republican from Conway, originally would have criminalized abortion after only six weeks, but the measure was amended in committee after other lawmakers objected.

"I'm disappointed for all of the unborn children that could have been saved in this bill, but I have faith that the 70 percent of the Legislature that voted to pass the bill will be there to override this veto," Rapert, founder of Holy Ghost Ministries, told reporters after the veto was announced, according to The Associated Press.

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