As European leaders prepare for an emergency summit in Brussels tonight, justice ministers have approved a sweeping package of anti-terrorist measures in response to last week's attacks in the US.
Minister for Justice, Mr O'Donoghue, said however that a number of legal and constitutional questions needed to be resolved before the measures could come into force.
The provisions include the creation of a European arrest warrant, obliging police in all 15 EU states to pursue suspected terrorists wanted in any member-state.
Extradition for terrorist offences would become automatic between member-states.
The ministers agreed to make a common definition of terrorist crimes and to impose minimum penalties for terrorist offences.
Europol, the European police network, is to set up an anti-terrorist unit and will be authorised to co-operate with US authorities.
Governments will review the removal of border controls between most EU states and security will be tightened on its external borders.
The ministers hope to implement the measures by early next year but Ireland, Denmark and the Netherlands may have to consult parliament before introducing them.
Mr O'Donoghue identified two potential difficulties under Irish law - the issue of "dual criminality" and a proposal to allow suspects to be arrested and detained at length for investigation, even if they are not charged.
But he expressed confidence that the issues could be resolved without changing the Constitution.
"I do not anticipate the necessity for a referendum," he said.
Under the Constitution, an Irish court cannot extradite a suspect for an offence that is not against Irish law.
The common definition of terrorist offences should resolve the difficulty but the Government is likely to insist that the definition is narrow and very precise.
It will be more difficult for the Government to agree to a European warrant for investigation but it is likely that other member-states will have similar objections.
EU leaders will discuss their response to last week's events and attempt to agree on a common approach to any US military action when they meet in Brussels this evening.
British Prime Minister Mr Tony Blair and French President Mr Jacques Chirac will report on their talks with President Bush in Washington this week.
Most EU states are members of NATO, which last week invoked Article 5 of its founding treaty, declaring that the attacks in the US represented an attack on the entire alliance.
All NATO members are obliged to help the US but individual governments may choose the nature and extent of that assistance.
Britain and France have indicated they will participate in a military campaign launched by the US. Germany has pledged "unswerving support".
After a meeting with Mr Chirac in Paris yesterday, Mr Blair dismissed suggestions that European support for the US was fading.
"One of the most important and significant aspects of what has happened in the days following those terrible attacks in the United States has been the strength, indeed I would say the growing strength of the coalition right around the world against terrorism," he said.
Mr O'Donoghue said he was unaware of any formal request to the Government from Washington for help during any planned campaign.
But he said the Government would seek to comply with any request.
The Government is understood to have decided in principle to accede to any US request to allow its military aircraft to fly over Irish airspace and to refuel at Irish airports.
