DUBLIN (Reuters) - The rival sides in Ireland’s decades-old battle over abortion made their final pitches to voters on Thursday, the eve of a referendum on liberalizing one of the world’s strictest bans on terminations.

Voters in the once deeply Catholic nation will be asked on Friday if they wish to scrap a prohibition that was enshrined in the constitution by referendum 35 year ago, then partly lifted five years ago for cases where the mother’s life is in danger.

Opinion polls have put those who favor changing the law in the lead. The two most recent surveys on Sunday showed the “Yes” side pulling slightly further ahead.

“This is a once-in-a-generation decision for the Irish people,” Prime Minister Leo Varadkar told reporters.

“It is an opportunity for us to change our country. If there is a ‘Yes’ vote, Ireland will still be the same place, just a place that is a little bit more compassionate, a little kinder and a little more understanding that it has been.”

“Yes” campaigners are urging voters to repeal the eighth amendment of the constitution, which equates the right to life of the mother with her unborn child’s.

They argue that with over 3,000 women traveling to Britain each year for terminations and others ordering pills illegally online, abortion is already a reality in Ireland.

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The “No” camp has seized on government plans to allow terminations with no restriction up to 12 weeks into a pregnancy if the referendum is carried, although that is not on the ballot paper.

They have suggested in recent days that if the referendum is defeated, the constitution could instead be amended again to allow for abortions in “hard” cases such as rape, incest and fatal fetal abnormality.

Varadkar and others say this is impossible - citing advice from Ireland’s Attorney General - and have accused their opponents of trying to dupe voters.

“If we ... vote ‘No’, no doubt this will come back in a year or two and then we can look at the hard cases, but not a carte blanche free-for-all for up to 12 weeks,” said Mattie McGrath, an independent lawmaker and prominent anti-abortion campaigner.

“If ‘No’ carries, the people will have spoken.”

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HOME TO VOTE

Most polls will open at 0600 GMT on Friday, although voting was already under way on Thursday on remote west coast islands.

Some expatriate Irish were flying home from as far as way as Bangkok, Los Angeles and Sydney to cast their ballots in a country that does not allow those abroad to vote via post or in embassies.

Those away for less than 18 months remain eligible to vote at their former local polling station.

The hashtag #hometovote was one of the top trending issues on Twitter on Wednesday, as it was three years ago when Ireland became the first country in the world to adopt gay marriage by popular vote.

Online comments suggested most of those heading home planned to vote “Yes”. Many posted photos of themselves wearing sweatshirts bearing the “Yes” side’s “Repeal” slogan.

“For me, I felt a moral obligation to come back,” said Ciaran Gaffney, 22, who forked out nearly 1,000 euros to return to the southwestern city of Limerick from Buenos Aires and bumped into four other returning voters on his flight home.

“As soon as the referendum was called, I just booked the flights there and then. My generation, my peers, are the ones who are going to be affected. I’m extremely excited to go into the polling booth and put that ‘X’ into the Ta (Yes) box.”