Proposals at the Convention on the Future of Europe involving mutual defence arrangements with other member-states have been firmly ruled out by the Minister for Foreign Affairs, Mr Cowen.
The Minister told the National Forum on Europe at Dublin Castle that a constitutional referendum would be required to approve a system of mutual defence within the EU.
Ireland was open to the idea of a "solidarity clause" whereby EU states would co-operate in response to emergency situations, but the Government would make a clear distinction between these arrangements and mutual defence.
"We should be open to the idea of a solidarity clause that would assist in the EU's response to emergency situations and new threats against civilian populations. Such a clause would enable all the instruments available to the EU to be mobilised, both civilian and military, within the territory of the Union, to avert the threat from terrorism, protect the civilian population and assist a member-state in dealing with the implications of a possible terrorist attack.
"This idea is broadly in line with our own approach. The other neutral and non-aligned members of the Union - Austria, Finland and Sweden - also support a solidarity clause along these lines.
"Suggestions for collective security arrangements, including the idea of a 'solidarity and common security clause', as supported by France and Germany, are more problematic. This could extend beyond emergency situations and represent a step in the direction of a mutual defence clause. It will be necessary for Ireland to maintain a clear distinction between emergency arrangements arising from natural or man-made disasters and any more 'hard defence' issues.
"As regards mutual defence, let me be absolutely clear. Ireland's constitutional position is unambiguous. Ireland cannot join a common defence without the approval of the Irish people in a referendum," Mr Cowen said.
The Fine Gael MEP for Munster, Mr John Cushnahan, had a procedural dispute with the chairman of the forum, Senator Maurice Hayes. Mr Cushnahan said a real opportunity to establish "a new equilibrium" in the relationship between the EU and the US after September 11th, 2001, had been lost because of the role played by the British Prime Minister, Mr Blair.
He was interrupted by the chairman, who said he would like to focus on the report of the convention's working parties on external action and defence, which were the topic of the day. Senator Hayes said: "I know you have to put it in a context, but I don't think it is helpful to attack the domestic policies of some other sovereign governments.
"The forum is there to develop and formulate Ireland's response to the thing, and I am rather anxious that it is not used as a basis for broad questioning of individuals in other states."
Mr Cushnahan said: "In order to argue why the EU should have a coherent viewpoint and the lessons we must learn, it is important to put it in context."He said Europeans should not be afraid to criticise US foreign policy, if they did so with one voice.