The Taoiseach has described as "horrific" the IRA's invitation to shoot the killers of murder victim Robert McCartney.
However, he said there was "a difference" between Sinn Féin and the IRA, adding "we have to keep going" with the peace process.
Speaking to reporters in Dublin early yesterday, Mr Ahern said he believed Tuesday night's statement from the IRA was "probably . . . the factual position" as the IRA saw it.
Nonetheless, he said, "It's an extraordinary statement . . . We all want to see justice being done. That their response to that was to eliminate three or four people is horrific."
Adopting a more conciliatory tone, however, Mr Ahern said: "While I am credited with the phrase, 'the IRA and Sinn Féin are the opposite sites of the one coin', there is a difference in circumstances.
"I have seen that in negotiations where Sinn Féin went to the IRA looking for issues to be approved.
"I do not think the people will be saying today that Gerry Adams wrote that statement. Neither do I think he wrote the second statement that came out after the robbery. So I think there are distinctions, and I am sure these issues are difficult for the leadership of Sinn Féin as well."
He said it was "not an extraordinary demand" for people to co-operate with the PSNI over the murder investigation.
"In this case, the IRA on their own admission, know precisely who is involved, and there are lots of witnesses."
Asked how difficult it was to move forward with the peace process following the statement, Mr Ahern replied: "When we heard the reports coming in yesterday that this statement was going to be made, those who work with me in the peace process didn't believe it. I am talking about public servants who have long experience of this. They just didn't believe it.
"So it is a shock but we have to keep going. If we are to get peace and justice, the rule of law, democracy - that requires us to end paramilitarism, to break the link, to end criminality; that is what we all want to do."
