The rejection of the European constitution by Irish voters in a referendum would "be an enormous setback for the country", the Taoiseach has warned.
The referendum will be held before the end of October 2006, Mr Ahern said yesterday, at the publication of information booklets on the constitution.
People, he believed, "want to be part of the economic, social, cultural dynamic that is Europe", he said, accompanied by the Minister for Foreign Affairs, Mr Dermot Ahern.
"To reject that and to reject the constitution would be an enormous setback in any country," he added, particularly since every "single Irish key interest" was protected.
Faced with previous treaty referendums, such as Maastricht, voters could identify issues they did not like "and say, 'I don't like this, or that, but I like the other,'" he said.
"When you put it into the constitution you are opposing the whole project. I do not hear people saying that," the Taoiseach said.
He travels to Rome today, along with the Minister for Foreign Affairs, for the formal signing of the treaty in the same room that hosted the Treaty of Rome signing in 1957.
"If you are asking me will I sign this in the belief that I can put my hand on my heart and say this is perfect for the Irish people, then the answer to that is yes.
"We got protection for every one of those major single issues that concerned Irish people, whether it was neutrality, tax harmonisation, or any other central issues," he said.
He said he could not see why people would oppose it, other than "to be against something for against's sake", or because political parties wanted to exploit the No vote.
He said he believed the public had much more information about the EU constitution than they had about past treaties, including the one agreed in Nice, "which was a dog's dinner".
The European Convention on the Future of Europe had publicly debated the constitution for months, while trade unions and others had been involved in its preparation.
Rejecting charges that Irish voters are not well versed in European issues, Mr Ahern said it was "always the case that people are not very well informed about Europe until it affects them".
But voters had shown themselves to be "the best informed people that I have ever come across", whether it is about "agriculture and ewes" or "the west of Ireland and bogs".
He accepted that the Government had mishandled the first referendum on the Nice Treaty: "I always recall those press conferences in Nice 1, when I could not enthuse any of yourselves, not to mind myself maybe," he said.
He refused to indicate when the referendum would be held, though he insisted that its timing would not be influenced by the referendum in the UK.
"We are more interested in having a well-informed debate and see how that turns out during 2005, and see what happens on the international stage.
"I am very anxious that we are not accused as we were accused in Nice 1 of not having a good debate. We need to make sure that we feed this information, and all of the other information, into the national psyche before we make up our mind. If we have done that by 2005, then perhaps we could have a 2005 date."
