(BRUSSELS) - Faced with the risk that Ireland might reject their cherished Lisbon Treaty, some top EU officials have cautiously broken Europe's collective silence to warn of the dangers that a 'No' vote could bring.

Concerned that their remarks might be misinterpreted, many leaders have kept a low profile but opinion polls in Ireland now show rising opposition to the blueprint, which is meant to streamline the way the EU operates as it expands.

In recent days, Luxembourg Prime Minister Jean-Claude Juncker -- Europe's longest-serving leader -- and the foreign ministers of Austria and France have warily stuck their heads above the parapet to defend the project.

While expressing hope the Irish would vote 'Yes' on Thursday, Juncker showed that he understood those tempted to reject the document by acknowledging that Europe's leaders are struggling to explain their vision to citizens.

"European issues have become extremely complicated and we use a language that is no longer understood. I believe that we should make an effort to speak the language of those we govern," he said Tuesday on a visit to Poland.

Austrian Foreign Minister Ursula Plassnik underlined that Ireland had "exploited very well the opportunities that a united Europe offers", a reference to Dublin's economic boom after joining the common market in 1973.

Her French counterpart Bernard Kouchner used similar arguments on Monday, when he told French radio that, in the case of rejection: "The first victims would be the Irish. They have benefited more than others."

European experts -- mindful of the crisis caused by French and Dutch rejections of the constitution three years ago -- are critical of such remarks, even though they differ little from those of Irish Prime Minister Brian Cowen.

Coming from the leaders of big EU members, they warn, the comments be seen as a diktat to a "small" country like Ireland.

"Shutting up would be the best thing we could do for the Irish and Europe," said a clearly angry senior official at the European Commission, the EU's executive body.

Kouchner stepped further out of line by referring to what could happen if the Irish vote 'No' -- as they did for the Nice Treaty in 2001 before passing it a year later -- while the official line has been that there is "no plan B".

France, which takes over the EU's rotating presidency for six months on July 1, would have to "go at it fiercely, go very quickly and try to convince the Irish," he said.

Yet in breaking this taboo, Kouchner had only said aloud what had been a corridor whisper: that Dublin could be invited to suggest adjustments to the treaty -- probably footnotes that would concern no one but Ireland.

This would allow a new version to be quickly submitted to the Irish people without interrupting the process of ratification, which should be more or less completed on Wednesday in 17 of the 27 EU countries.

Indeed, so determined is France to take the project forward that President Nicolas Sarkozy has made it the priority of his EU presidency.

He already plans to supervise the political wrangling on the prestigious posts created by the Lisbon Treaty; that of a more permanent EU president and more powerful foreign policy supremo.

And the French head of state commissioned German Chancellor Angela Merkel this week to help him should Ireland decide 'No'.

"Whatever happens, the reaction will be a Franco-German one," Sarkozy said, in an effort to show that Europe's historic driving engine will be ready come what may on Thursday.

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