Taoiseach Bertie Ahern has called for a debate on EU enlargement before any new members are chosen.
At the European Council meeting in Brussels, Mr Ahern said Ireland had supported Romania, Bulgaria, Croatia and Macedonia's bids for EU membership but the time had come for a process of reflection on how big the union could grow.
"I think the work has to be done, we are already up to 27, and maybe 29 [ members], so it will have to be looked at after that before we go any further," said Mr Ahern.
He said "people will have to look at the figures".
Mr Ahern made his comments following the decision of the European Council to grant the Former Yugoslav Republic of Macedonia candidate status to join the EU.
However, the written conclusions of the summit also included a reference to the need for a debate on enlargement before further steps toward full membership were taken. France and several other members sought this reference as states such as the Ukraine, Bosnia and Serbia seek closer EU ties.