Updated

Democratic Gov. Mike Beebe on Tuesday vetoed a ban on most abortions in Arkansas at 20 weeks into a pregnancy, setting up an override fight with a Republican-controlled Legislature that has been pushing for more restrictions on the procedure.

Beebe said he vetoed the ban, which is based on the disputed belief that a fetus can feel pain at 20 weeks, because it runs afoul of the U.S. Supreme Court's 1973 Roe v. Wade ruling that legalized abortion until the point where fetuses can survive outside the womb, usually at 22 to 24 weeks. The Republican sponsor of the measure said he'll seek to override Beebe's veto.

"Because it would impose a ban on a woman's right to choose an elective, nontherapeutic abortion before viability, House Bill 1037, if it became law, would squarely contradict Supreme Court precedent," Beebe said in his veto letter. "When I was sworn in as governor I took an oath to preserve, protect and defend both the Arkansas Constitution and the Constitution of the United States. I take that oath seriously."

Beebe also cited the cost of a potential lawsuit if the state enacted the ban. The American Civil Liberties Union of Arkansas has said it would likely sue if it went into effect.

Beebe's veto comes as Arkansas lawmakers are weighing stricter legislation that would prohibit abortions at 12 weeks into a pregnancy. Beebe has said he has concerns about that legislation's constitutionality as well. That measure is expected to go before a Senate panel Wednesday.

Rep. Andy Mayberry, who sponsored the 20-week ban, said he was disappointed with Beebe's decision and would ask the House and Senate to override the governor's veto. It takes a simple majority in both chambers to override a governor's veto. Republicans hold 51 of the 100 House seats and 21 of the 35 Senate seats.

Beebe announced the decision shortly after Mayberry, R-Hensley, met with the governor and tried to alleviate his concerns about the bill.

"Apparently he and I have differing opinions on that bill," Mayberry said. "We'll enter into the next phase of the legislative process."

Seven states have enacted similar 20-week restrictions, according to the Guttmacher Institute, which tracks laws affecting women's health. A similar law in Arizona has been blocked while a federal appeals court reviews a lawsuit challenging it.

In his letter, Beebe cited concerns about the cost of a similar challenge. He wrote that Arkansas had to pay nearly $148,000 in attorneys' fees to the plaintiffs in a lawsuit challenging a 1997 late-term abortion ban that a federal appeals court overturned.

"Litigation fees and costs have increased extensively since then," Beebe wrote. "The taxpayers' exposure, should HB1037 become law, will be significantly greater."

Mayberry's bill included exemptions for rape, incest and the life of the mother. Opponents have criticized it for not including exemptions for fatal fetal conditions.

Mayberry said he was confident he would have the votes to override Beebe's veto. The House approved Mayberry's bill on an 80-10 vote last week. It had been previously approved by the Senate on a 25-7 vote.

Abortion rights advocates who had gathered at the Capitol cheered when Beebe's decision was announced

"I am very grateful that the governor understood that it's not reasonable for the government to interfere with these very private and complex medical decisions that a woman needs to make with her doctor and with her faith and with her family," said Jill June, president and CEO of Planned Parenthood of the Heartland. "The decision to end a pregnancy is one of the most complicated decisions a woman will make in her life."

The bill marks the 11th time Beebe has vetoed legislation since taking office in 2007.

Beebe, who is serving his second term, has backed some abortion restrictions, including a bill signed earlier this month that bans insurers participating in the exchange created under the federal health care law from covering most abortions. Two years ago, he signed into law a proposal placing new regulations on the clinics that offer the abortion pill and in 2009 he signed legislation that mirrors a federal law banning late-term abortions.