As Ireland took over the EU's revolving six-month presidency, the Taoiseach Bertie Ahern said the country's motivating force will be to build a consensus.
At a ceremony at Dublin Castle to formally mark the occasion, attended by members of the cabinet and the diplomatic corps, Mr Ahern said Ireland will be even-handed and open.
Ireland faces handling the aftermath of the collapse of talks on Europe's constitution.
The Taoiseach also said the EU will undergo a profound transformation during the Irish presidency, when 10 Mediterranean and Eastern European countries join in May.
Mr Ahern said a major event will be held in Dublin to mark the biggest expansion in the EU's history.