Last push for votes as EU leaders warn over Brexit

Just hours before polling booths open, European Commission chief Jean-Claude Juncker and France's president stepped in to warn there would be no turning back if voters endorsed a Brexit on Thursday.

"Out is out," Juncker told reporters in Brussels, dismissing any talk of renegotiation after a "Leave" vote, while Francois Hollande stressed an exit would be "irreversible".

German Chancellor Angela Merkel was more measured, saying she wanted Britain to stay but that the decision was down to Britons.

Opinion polls indicate a tiny lead for the "Remain" camp led by Prime Minister David Cameron, four months after he announced the date for the vote, but the result is on a knife-edge.

Britain would be the first country to leave the EU in the bloc's 60-year history, dealing a hammer blow to a union already battling with an unprecedented migrant crisis.

Better together

The prime minister, who faces calls to resign if he loses, spent the final day of campaigning criss-crossing Britain on a battle bus and doing interviews.

"If I had to sum up this whole campaign in a word, it would be that word 'together'," Cameron told BBC radio.

Out on the campaign trail, he said: "If we want a bigger economy and more jobs, we are better if we do it together".

"We're better able to fight challenges from terrorism and climate change, we're better able to drive good trade deals with China and America."

Bosses from nearly 1,300 of Britain's leading businesses signed a letter in The Times saying the country was stronger in the EU, while James Bond star Daniel Craig and Irish rock band U2 became the latest celebrities to back "Remain".

Bookmaker Betfair said their latest odds implied a 76 percent chance of "Remain" winning.

Some 51 percent of voters back "Remain" versus 49 percent for "Leave" among those who have decided, according to an average of polls compiled by What UK Thinks.

'Country is a mess'

Cameron's main rival in the "Leave" campaign and possible successor, Boris Johnson, said Britain stood on the brink of "independence day" from Europe.

"I do think that we are on the verge, possibly, of an extraordinary event in the history of our country and indeed in the whole of Europe," Johnson said in eastern England.

Nigel Farage, leader of the anti-EU UK Independence Party, said: "I genuinely belive we are going to win this."

A British withdrawal would trigger a lengthy exit negotiation, leading to the loss of unfettered access to its partners in the 28-nation market and forcing the country to strike its own trade accords across the world.

In Europe, the referendum has raised concerns of a domino effect of exit votes that would imperil the integrity of the bloc, already buffeted by the eurozone and migration crises.

Though many voters fret over the financial consequences of a Brexit, others relish the prospect of taking back power from Brussels and reining in high levels of immigration.

"I think we need to make our contribution to Europe and to the global economy. And the best way we can do that is by being in it, not by ignoring it," Chet Patel, a 44-year-old telecoms worker told AFP.

Pat Hand, a 50-year-old construction worker, said he would be voting to leave the EU.

"The country is in an absolute mess. I work in construction and every single person on my job is not English," he said.

Questions about how soon Turkey could join the EU, opening the door for hundreds of thousands of new migrants to Britain, have been central to the "Leave" campaign.

Sources told AFP that the EU planned new membership talks with Turkey in a few days to open a new chapter on finance and budget affairs.

Turkey has so far completed only one of 35 chapters needed to join the bloc.

Marking slain MP's birthday

The "Leave" campaign briefly took a slight lead in many opinion polls until last week, sending sterling plummeting.

This fell away after campaigning was paused for two days following Thursday's killing of pro-EU lawmaker Jo Cox of the main opposition Labour party.

Wednesday would have been her 42nd birthday and a series of commemorative events were being held in Britain and around the world.

Cox's widower Brendan said his wife, who was particularly noted for her work on refugee rights, had been killed because of her political views.

"She worried about the tone of the debate... The tone of whipping up fears and whipping up hatred potentially," he told the BBC Tuesday.