The Belfast Agreement must endure even in the event of a united Ireland, a nationalist leader claimed tonight.
SDLP leader Mr Mark Durkan said on the eve of the publication of the statistics on religion in the 2001 census that it should not surprise people if the Catholic community has grown.
"The census is likely to paint a picture of a changing Northern Ireland," the Foyle MLA said.
"But it does not come as a surprise - the reality is that the nationalist vote has been growing steadily over the last few decades.
"Nobody can say with certainty that this will lead to the united Ireland that the SDLP seeks.
"But we can be certain that there will be a united Ireland if a majority votes for one and the south agrees. That is the position of the Agreement and it is the position of the SDLP."
Speculation has been mounting in recent days that the gap between the Protestant majority community in Northern Ireland and the minority Catholic community will be reduced significantly.
Those rumours were fuelled tonight by an alleged Irish government document leaked to Ulster Television which predicted that the Protestant population would, for the first time, fall below the 50% barrier when the census figures were released.
Northern Ireland Office officials and representatives of the Statistics and Research Agency in the Province have been tight-lipped about the findings of the survey.
However, political parties will be paying close attention to the results and will be interpreting their significance for the constitutional future of Northern Ireland.
Under the Belfast Agreement there is provision for a border poll deciding if Northern Ireland should remain within the United Kingdom or be part of a united Ireland.
Mr Durkan said tonight that it was vital people were certain that Irish unity did not mean an end to the provisions and protections of the Good Friday Agreement.
"For whatever change the future brings, some things will remain the same," he said.
"Nationalists and Unionists will still face the challenge of sharing our society together as partners and as equals.
"The Belfast Agreement offers us the template for doing this. That is why at the Forum for Peace and Reconciliation the SDLP is working for a consensus that all the Agreement's arrangements, assurances and accommodations will endure in a united Ireland."