Ahead of his visit to Dublin today, European Commission President Mr Romano Prodi said EU enlargement can proceed without the Nice Treaty.
Mr Prodi admitted his concern at Ireland's rejection of the treaty and said he would listen to Irish voters during his three-day visit.
In an interview in today's Irish Times, Mr Prodi said the issues of enlargement and the ratification of the Nice Treaty should be treated separately.
Under the Amsterdam Treaty of 1998, the EU can accept up to five new members, making a total of 20. But Mr Prodi said the EU could accept more than five new member-states without ratifying Nice.
"Legally, ratification of the Nice Treaty is not necessary for enlargement. It's without any problem up to 20 members, and those beyond 20 members have only to put in the accession agreement some notes of change, some clause. But legally, it's not necessary.
"This doesn't mean the Irish referendum is not important. But from this specific point of view, enlargement is possible without Nice," Mr Prodi said.