The Irish government said it hoped voters would back the European Union's reform treaty but the race was very close before Thursday's referendum.

A survey last week put opponents of the Lisbon Treaty, which replaces a constitution rejected by French and Dutch voters in 2005, ahead for the first time.

Ireland is the only one of the 27 member states holding a referendum - meaning a country accounting for less than 1 percent of the bloc's 490 million population could derail a pact designed to reform how it is run.

"We believe that certainly that in the last 72 hours, probably a little longer now, there has been a very strong move back towards 'Yes'," said Ireland's EU minister, Dick Roche, citing results from canvassing by his own Fianna Fail party.

The last survey of the campaign, carried out by Red C and published at the weekend, showed opponents of the treaty gaining ground but put the "Yes" vote slightly ahead.

"I would say it is very close but edging towards a 'Yes' depending on who goes out to vote," Red C Managing Director Richard Colwell told Reuters on Wednesday.

Colwell said it was "too close to call" but that the "Yes" camp may have the edge because large numbers of voters opposed the treaty simply because they did not understand it, meaning there was a good chance they might not turn up to vote.

As people headed to work on Wednesday, many of them clutching newspapers calling for a "Yes" vote, bank worker Tony Connell, 42, said he had would be voting "No" on the treaty as he had "no idea what it means".

Margaret O'Sullivan, a civil servant, said the benefits of EU membership had persuaded her to vote "Yes", even though she did not fully understand the document.

Most parliamentary parties, business, the congress of trade unions and a powerful farming lobby have campaigned for a "Yes" vote, but they acknowledge the complex treaty text has made it difficult to convince voters.

BONDS VULNERABLE

Critics of the treaty such as the nationalist Sinn Fein party, argue Brussels is trying to bully Irish voters into accepting a treaty that they fear will endanger Ireland's democratic rights and traditional military neutrality.

Ministers have said the Irish economy, which has gained enormously from EU membership, would suffer if the treaty was rejected - especially when it is already reeling from a property downturn and the credit crisis.

EU support helped underpin Ireland's "Celtic Tiger" economic boom, which began in the 1990s and transformed one of Western Europe's poorest countries into one of the world's richest.

Opponents say the treaty will allow the EU to force Ireland to raise low corporation taxes, which have drawn investors to Ireland and encouraged companies such as Google and Yahoo to set up their European headquarters in Dublin.

Nine out of 10 Dublin-based economists polled by Reuters last week said a "yes" vote would be the best result for future prosperity, helping to safeguard investor confidence.

One of the nine analysts, Bloxham's Alan McQuaid said on Wednesday that Irish government bonds would likely be hit most by a rejection, though he saw no long-term negative impact for Irish stocks.

"A rejection of the treaty is unlikely to blot the economic landscape in Ireland or Europe but the optics are important to external audiences, especially as Ireland has marketed itself to overseas investors as very much being part of Europe," he said.