Sinn Féin president Gerry Adams has challenged the Democratic Unionist Party to take the "difficult" decision to enter dialogue with republicans.
He said the Rev Ian Paisley's party might find it "a very uninviting prospect", but their current position of not negotiating with Sinn Fein was not sustainable.
Mr Adams said he awaited a positive response from the IRA to his appeal for them to declare a purely non-violent democratic future - and said there was now an unprecedented opportunity to make political progress in Northern Ireland.
In a direct message to the DUP, he said their electoral successes had given them the leadership of unionism and they could not opt out of their responsibilities.
"Their increased mandate brings with it increased responsibility and an imperative to deliver for their electorate. The DUP needs to engage in a meaningful way in the political process and that means engaging, negotiating and talking with Sinn Fein," said Mr Adams.
He conceded: "The DUP may find that is a very uninviting prospect," adding: "We can all find excuses not to engage."
Sinn Féin, said Mr Adams in a statement, recognised and respected the DUP's mandate and knew that a necessary element of any conflict resolution process was the primacy of inclusive, unconditional dialogue.
That demanded a serious, good faith effort to engage with political opponents, he said.
"Dialogue with political opponents may be difficult, as much for Sinn Fein as for the DUP, but dialogue is the only way forward, the only way to build a lasting peace.
"The public position of the DUP is unsustainable. At some point the DUP will have to enter the world of real politics. How else do they hope to deliver for their electorate?"
PA