Sinn Fein national chairman Mr Mitchel McLaughlin has told a conference in Stormont that there will be a united Ireland and the task of all "sensible" Irish political leaders should be to prepare for unification.
Mr McLaughlin added that unionists must be shown that Irish republicanism is a "fundamental part of their future".
Speaking at the Building for Irish re-unification conference, Mr McLaughlin said the Belfast Agreement is about "a new political dispensation on the island of Ireland and a new relationship between Ireland and Britain".
"Strand 2 - the All Ireland framework - creates a dynamic that some have attempted to frustrate and dilute.
"But it has also seen much progress and pragmatic, even positive, responses from across the political spectrum. For Irish republicans there is clearly a focus on Strand 2 and on consolidating and developing the All Ireland architecture."
Mr McLaughlin said Sinn Fein's republicanism was about change - "fundamental, deep-rooted change".
He said engagement with unionists is vital in order to to build on the momentum for Irish re-unification.
"We have to show unionists that Irish republicanism is a fundamental part of their future. That together we can build a future of equals on this island that empowers, protects and enriches everyone."
"There will be a united Ireland," Mr McLaughlin said. And our task, and that of all sensible Irishpolitical leaders, should be to prepare for reunification. This is a challenge not just for Sinn Féin and republicans and nationalists but also for the unionist community and leadership of Unionism."
Sinn Fein TDs, MPs, MLAs, councillors and members from all over Ireland are meeting to discuss what Mr McLaughlin said were the strategies needed to "consolidate the All-Ireland architecture and the momentum for Irish re-unification".