The Taoiseach Mr Ahern said this afternoon that the there was a "50/50" chance of striking a deal on a new European Union constitution before the end of June, when Ireland's six-month presidency ends.
Mr Ahern, who has been touring European capitals since early May seeking consensus on a draft constitutional treaty ahead of a crucial summit on June 17th and 18th, he believed talks would go down to the wire.
"I still think it's 50/50, there are large issues. Trying to get 25 countries to agree on issues that are fairly fundamental to them is difficult," said Mr Ahern, speaking from Guadalajara, in Mexico, where he was attending an EU-Latin America summit.
"At the end of the day the only ones that will make decisions are prime ministers, and they'll only make it when we are up against the clock, I wish it wasn't that way, but that's the way it will be."
A new constitution for the EU is seen as vital for the smooth running of the bloc, which expanded to 25 members from 15 on May 1st.
A previous attempt to approve the constitution in December collapsed in a dispute pitting medium-sized states Poland and Spain, which wanted to preserve outsized voting rights won in
the 2000 Nice treaty, against heavyweights France and Germany.
Mr Ahern said Britain had concerns over justice and internal affairs and added: "Some countries, like the Netherlands and Germany, have problems with financial perspectives and other issues, every country has a problem with something."