The British and Irish governments should lead the way in the search for a "big deal" to end the crises in the peace process, Sinn Féin has said.
Mr Martin McGuinness, speaking after the Taoiseach's blunt warning, said Dublin and London had to work in tandem with all pro-agreement groups to oppose "malign elements".
He said: "A comprehensive approach is required. The Sinn Féin leadership will do everything in its power to make our contribution to that."
He added: "There are dissident activities out there. There are people in society who are involved in punishment beatings who are not republicans."
Mr McGuinness restated his party's view that the forthcoming European and local government elections in the Republic explained much of the focus on alleged republican paramilitary activity.
"We shouldn't let elections interfere in the work of the peace process. It is more important than any election," he said. No one in his party would run away from the challenges outlined by Mr Ahern.
"The vast bulk of violence that we have experienced over recent years has come from unionist paramilitaries."
Describing the DUP as "a party in transition" he forecast that the Rev Ian Paisley's party would eventually agree to share executive power with Sinn Féin.