Speaking at the start of a two-day European forum of the Bertelsmann foundation, Barroso said that after the admission of Bulgaria and Romania, there would be no new full members without new institutional frameworks.
Speaking of negotiations which had already started, Merkel said they could be concluded once all conditions had been met. She added that an important criteria for the full membership of those countries, namely Croatia and Turkey, would be the EU's capability for new enlargement as defined by the Copenhagen charter.
The Bertelsman international forum is an annual conference which pools leading European and world politicians, business people and public figures.
Attending this year's forum, which addresses the EU's future, are the state secretary at the Croatian foreign ministry, Marija Pejcinovic-Buric, and Croatia's Ambassador to Germany Vesna Cvjetkovic-Kurelec.