The Taoiseach has welcomed the British Prime Minister's pledge to match the Republic's proposed new anti-terrorist legislation when the House of Commons is recalled next week.
As he prepared to meet Mr Blair this morning in Mayo, Mr Ahern said the enhanced co-operation between the governments was aimed at "the small dissident groups seeking, without regard to humanity, to undermine the Good Friday agreement".
He added: "The fact that the parliaments of Dublin and London are specially recalled for the same dates symbolises effectively the shared determination of the two governments to deal decisively with any groups who persist in violence in defiance of the clear will of the people of the island."
Other Government and Opposition spokesmen also welcomed Mr Blair's announcement. The Minister for Justice, Mr O'Donoghue, said it was proof that the governments were moving in tandem against the extremists opposing the Belfast Agreement with violence: "I don't believe the legislation can be effective unless we move in parallel, and that's what we're doing."
He said he was not surprised that the British government had not moved to return internment to the statute books.
"What's important is that whatever is done is effective. If it was decided later on that the route that has been chosen wasn't working, then clearly it would be open to the British government to introduce legislation allowing for the reintroduction of internment at that point."
The Minister of State at the Department of Foreign Affairs, Ms Liz O'Donnell, welcomed "the matching of the measures we announced last week", which she said were a response to "a specific security situation" and balanced the responsibilities of both governments to protect civil rights.
Fine Gael's spokesman on Northern Ireland, Mr Charles Flanagan, warned that legislation alone would not solve the problem. Welcoming the British proposals, he called for a level of co-operation between the Garda and the RUC "that would leave nothing to chance." He added: "Some form of joint patrolling should not be ruled out."
After meeting Mr Blair, the North's First Minister, Mr David Trimble, said he welcomed the recall of Parliament. The Deputy First Minister, Mr Seamus Mallon, said all legislation should by definition be short-term.
But Sinn Fein's chief negotiator, Mr Martin McGuinness, described the security measures as a mistake. Sinn Fein believed the proposals were a retrograde step, he said.
"We believe that the history of Ireland has shown, particularly over the last 30 years, that there have been many miscarriages of justice. I think many people will see today's announcement as an attempt by the British government to introduce internment under another guise." Mr McGuinness was speaking on his way into a meeting with Mr Blair at Stormont.
Earlier, before the announcement, Mr McGuinness said he believed the proposed measures were an "over-reaction". "The RUC, in the eyes of many nationalists in Northern Ireland, is the most discredited police force in the whole of western Europe. To give the RUC that power at a time when its whole future is in question in relation to the outcome of the Good Friday agreement, is crazy," he said.
However, the measures were described as "too little, too late" by the Ulster Unionist MP, Mr William Thompson. He welcomed the announcement that a suspect could be convicted of membership of a proscribed organisation on the word of a senior police officer. But he said it was still "not a good enough way of dealing with the real problem of terrorism."
Mr Thompson, whose West Tyrone constituency includes Omagh, said Mr Blair should restore to the statute book the power of internment which was already law in the Republic. He criticised Mr Blair's statement that only stipulated groups would be affected by the crackdown. "You can rest assured it will not apply to the Provisional IRA or Sinn Fein.""
The Irish Republican Socialist Party said the new measures would prove counter-productive and "an abuse of civil liberties".