Mississippi's Republican governor, Haley Barbour, says the life-at-fertilization initiative on next Tuesday's state ballot is "ambiguous" and he's not sure whether he'll vote for or against it.

Initiative 26 seeks to amend the state constitution to declare that life begins when a human egg is fertilized.

Speaking with reporters Wednesday after a speech in Jackson, Barbour said he opposes abortion but thinks the initiative could have unintended consequences if it passes. For example, he said it's unclear whether the measure would hamper in vitro fertilization or limit medical treatment for women with ectopic pregnancies _ concerns that have also been raised by physicians' groups, including one that represents Mississippi obstetricians and gynecologists.

"What's been put on the ballot is a little bit ambiguous," said Barbour, who weighed a presidential bid in 2012 but decided against it.

Barbour, who leaves office in January after two terms, said he believes life begins at conception, but he thinks that's different than what the initiative asks.

"It doesn't say life begins at conception. It says life begins at fertilization, cloning or the functional equivalent thereof _ something to that effect," Barbour said. "Some very strongly pro-life people have raised questions about the ambiguity and about the actual consequences _ whether there are unforeseen, unintended consequences. And I'll have to say that I have heard those concerns and they give me some pause."

The initiative is backed by a Colorado-based group, Personhood USA, which is seeking to put similar life-at-fertilization measures on ballots in 2012 _ in Florida, Montana, Ohio and Oregon. Keith Mason, co-founder of Personhood USA, said the group ultimately wants to add such an amendment in the U.S. Constitution.

If the Mississippi initiative passes Tuesday, it would become part of the state constitution 30 days after the election results are certified, probably by mid-December. Supporters say that if that happens, they expect it to be challenged in court and that challenge could become an attempt to overturn Roe v. Wade, the 1973 U.S. Supreme Court decision that established a legal right to abortion.

The initiative is endorsed by both candidates in a governor's race that's also being decided Tuesday, Republican Phil Bryant and Democrat Johnny DuPree.

Barbour _ who cannot seek a third term as governor because of term limits _ has been praised in the past by anti-abortion groups. He said he wishes the "personhood" issues would've been handled through the Mississippi Legislature rather than in an initiative.

"I don't want the pro-abortion people of the United States to look at Mississippi and say, `They didn't vote for what was pro-life,'" Barbour said. "But at the same time I look at people, there are right-to-life organizations, the Roman Catholic church, the bishops, who are very concerned about this. Some of them have come out against it."

The proposed amendment has caused a rift among Mississippi religious groups, doctors and other health groups, and among abortion opponents.

Among the physicians supporting the "personhood" initiative is Dr. Freda Bush, an obstetrician-gynecologist in Jackson. She has said opponents are using scare tactics and she believes the measure would help protect women and babies.

"It will begin to restore a culture of life from conception to natural death," Bush said in September.

"What will personhood accomplish?" Bush said. "Simply, it will acknowledge the pre-born as a person by love and by law. Will personhood end abortion in Mississippi? Yes. Because we believe abortion is the taking of an innocent human life."

Dr. Randall Hines of Jackson, an IFV specialist, said last week that physicians "don't need the state government to help us decide how to take care of our patients."

"We have our patients' best interests at heart, and we want our patients to decide what is best for them. We do not need a judge or a legislator deciding that for us."

Hines said he believes the initiative could limit treatment for infertility and outlaw some forms of birth control such as the intrauterine device. He said legislators or judges could decide whether other forms of birth control, including the pill, would become illegal if the amendment passes.