Northern Ireland's future could be bleak unless all political parties work together to reach agreement, the Taoiseach, Mr Ahern, said today.
The Taoiseach said the power-sharing executive must be restored to avoid another period of conflict.
"The danger is that the Assembly isn't working. If there is no executive, no sense of ministers working collectively then there is no political system," he said.
"The risk is that people will take back to the streets in one form or another and that's a risk that is too great.
"If you were to have that kind of frustrated period and rejectionist period that I hope we do not see, then the future would be bleak and you would inevitably get back into some kind of conflict, let us hope it wouldn't be violence.
"No society operates without its elected administration," he added. Speaking on BBC1's Breakfast with Frost programme, Mr Ahern said that the troubles and violence must be consigned to the past and political parties must move forward.
"In peace processes all around the world there is never status quo but if there is static, they go backwards," he said.
"It's been six years since the Good Friday Agreement and we'd always built in a mechanism for review." Acknowledging that the configuration of the parties had changed, he said parties now had to focus on what changes could make a partnership Government work.
"The will of the people is that we should have an Assembly and an Executive," he said.
"There is a major responsibility on all of the parties in Northern Ireland to work with us in the early months of 2004 to find resolutions to these complex issues."
PA