Taoiseach Bertie Ahern is travelling to Berlin today to take part in ceremonies marking the 50th anniversary of the Treaty of Rome.
The treaty established the European Economic Community (EEC) and was signed by France, West Germany, Italy, Belgium Netherlands and Luxembourg.
Ireland joined the economic bloc in 1973, during the first expansion of the EEC. Denmark and the United Kingdom also joined that year, followed by Greece in 1981, Spain and Portugal in 1986 and Austria, Finland and Sweden in 1995.
To mark the anniversary, festivities have been staged around Europe and Berlin, which is hosting two days of street parties, nightclub events and museums will host exhibitions into the evening.
Veteran rocker Joe Cocker will take to the stage today by the Brandenburg Gate, symbol of Europe's post-World War Two split before the 1989 fall of the Berlin Wall.
EU leaders attended more demure events last night including a Beethoven concert and a slide show of images of the earth taken from space presented by German astronaut Thomas Reiter. Germany is the current president of the European Union
German Chancellor Angela Merkel asked fellow European leaders for their support today as she presses ahead with a revival of the bloc's constitution, saying failure to move the bloc forward would be a "historic error".
Ms Merkel said the 27-nation club needed new dynamism two years after French and Dutch voters rejected a charter to overhaul the bloc's creaking institutions.
"It is important and necessary that today, here in Berlin, 50 years after the signing of the Treaty of Rome, we are united behind the goal of putting the European Union on a new common foundation by European parliamentary elections in 2009," Ms Merkel said according to the text of a speech.
"I will work to ensure that by the end of the German presidency a road map can be agreed and I am relying on your support for this," she said.
"I am convinced that it is not only in Europe's interests, but also in the interests of the member states and citizens that we succeed. Failure would be a historic error."