National fears over competition from the new EU member states must be rebutted "clearly and convincingly", the Taoiseach has said.
Speaking about the No votes in both France and the Netherlands against the European Constitution, Mr Ahern said that in national debates, voters were expressing fears that their jobs are under threat from low-cost producers in the new states.
Mr Ahern said, however, that the accession of 10 new countries to the EU on May 1 stlast year represents "an unprecedented" opportunity" for the EU and not a threat.
The Taoiseach was delivering a lecture entitled Europe Our Common Future at Humboldt University, Berlin.
Mr Ahern said the current crisis in the EU would be surmounted through "leadership and determination".
"Ireland as a loyal and committed member of the Union will do whatever we can to steady the process and manage the current difficulties in a positive and constructive way."
He urged that "at all costs, we must now avoid pessimism and overreaction" but said that what the French and Dutch electorate had said should be listened to.
He added: "We should listen to our people. If we do so, I have no doubt that we will find the collective wisdom and resolve to chart the best course ahead."
Mr Ahern said Ireland had published a Bill providing for a referendum on the constitution and was continuing its preparations for the ballot.
"We will, of course, take into account the outcome of the discussion at the forthcoming European Council. At the Council, the heads of state and government will need to consider carefully how best to approach the completion of the ratification process."