Dr Ian Paisley's Democratic Unionists are basing their election strategy on a call for a new agreement to replace the Good Friday accord.
In its first televised election broadcast last night, the party said the 1998 agreement could not work because it was not sufficiently inclusive. Pledging to build working arrangements between unionists and nationalists, the party is offering to negotiate a new deal.
However, Sinn Féin criticised anti-agreement unionists, accusing them of fooling the electorate with claims that the Belfast Agreement can be renegotiated.
Mr Martin McGuinness, unveiling a Sinn Féin election billboard in south Belfast yesterday, said the DUP was "trying to fool the electorate about their ability to renegotiate the Good Friday agreement after this election. That is not going to happen and I think there are people in the party who know that."
He repeated his belief that real progress was made with the Ulster Unionist leader, Mr David Trimble, during protracted negotiations this month.
"That progress must be built upon," he said.
The SDLP leader, Mr Mark Durkan, was campaigning in North Down yesterday.
Predicting that the SDLP would pick up a seat, Mr Durkan said his party offered: "No spin, no stunts - just straightforward representation on key issues."
He said all North Down supporters of the Belfast Agreement should vote "for the party that has lived up to it".