The Minister for Foreign Affairs, Mr Cowen, has underlined the need for ratification of the Treaty of Nice.
During the Nice referendum last June, some on the No side had suggested five new member states could be admitted without treaty change, but it was now clear that negotiations with 10 applicants would likely conclude simultaneously.
It was "crystal clear" that failure to ratify Nice would be to place a "serious obstacle" in the way of enlargement, the Minister said.
