GERRY Adams has accused the DUP of failing to take a positive approach to political talks about Northern Ireland peace process issues.
The Sinn Féin president blamed the challenge from those on the "extreme right" of unionism opposed to concessions and said the party's partners in government at Stormont had failed to face down so-called rejectionists.
"Two weeks ago party leaders in the north agreed to re-engage in intensive talks around these issues," Mr Adams, speaking at the annual Wolfe Tone commemoration at Bodenstown, Co Kildare, said.
"Since then, however, we see no evidence that the DUP is willing to approach this process in a positive, constructive way.
"This is all to do with what is happening within political unionism."
Mr Adams told the republican commemoration that the DUP and UUP adopted the St Andrews and Hillsborough peace process-related political agreements but were being challenged by those on the more extreme right like the Traditional Unionist Voice and Ukip.
"This is a consequence of the huge failure by the UUP and the DUP to face down these rejectionists in the same way as Sinn Féin has done with anti-Agreement elements on the fringes of republicanism," he said.
"Let me be clear - Sinn Fein will continue to stretch out the hand of friendship to our unionist neighbours. We will uphold everyone's civil and religious rights.
"But we will also stand firmly and robustly against the bigots, the racists and the sectarian fundamentalists. They and their political cheer leaders are on the wrong side of history.
"Change may be delayed but it can not be stopped."
The renewed bid for a political settlement within weeks comes six months after marathon sessions chaired by former US diplomat Richard Haass ended without agreement and only weeks before the loyal order parading season,
which in recent years has sparked rioting in north Belfast, gets into full swing.
The negotiations are in part an effort to avoid violence which has characterised annual Twelfth of July loyal order demonstrations in north Belfast.