Mr Martin McGuinness, the Sinn Fein Mid-Ulster MP, has called on republican paramilitary dissidents to end their violence and campaign for a united Ireland by "peaceful" means.
At a press conference in Belfast yesterday, the Sinn Fein president, Mr Gerry Adams, also expressed regret and sorrow to victims of republican violence.
Ahead of the special Sinn Fein ardfheis on Sunday called to change radically the party's constitution, Mr McGuinness insisted yesterday the party was united. There was "a tiny number of discordant voices" within republicanism but they would not dictate Sinn Fein strategy.
Criticising recent violent actions by republican dissidents, he added: "The people who are involved in these acts at this time are doing a great disservice to themselves, to their families, to their communities, and are doing a great disservice to all the people of Ireland.
"I believe political leaders - people who have political notions or thoughts in their head - have a responsibility to try to bring about in a peaceful way the achievement of the Irish republic," he said.
Mr McGuinness said he was "supremely confident" republicans would remain united and support on Sunday the leadership's proposals for a Yes vote in the referendums, North and South, and for Sinn Fein politicians to be allowed take seats in the Northern Assembly.
"We are facing into this with great confidence in our ability and in the people who form the Sinn Fein organisation.
"I think we will see a sensible, well-rounded debate next Sunday, and out of that you will see Irish republicans continuing with the work to move to the Irish republic we are all seeking," said Mr McGuinness.
Mr Adams also expressed confidence that despite some ardfheis resolutions opposing the agreement, the delegates will support the leadership's proposals. He described the shift in republican policy as "historic" and a "watershed".
The leadership was calling for a Yes vote "in the context of our absolute rejection of partition, of the unionist veto, and of British rule", he added.
Mr Adams said Sinn Fein remained "totally wedded" to its "peace strategy". He acknowledged some republicans would have difficulties with the proposals. "Peace requires change and change, as we have said many times, presents difficulties and creates trauma."
He also appeared to go further than in the past in expressing regret for republican violence. "We want to see an end to all killings and we have worked energetically to bring this about. I have said many times that I regret and indeed I am sorry that so many people have been killed.
"I have acknowledged the hurt which republicans have inflicted," said Mr Adams.
But he complained of a lack of balance "on these difficult matters". This was "deeply hurtful" to those who were victims of the British army or RUC "as a result of the overt actions of the British crown forces on our streets or the covert actions of their dirty tricks or military intelligence units."
On unionist demands for decommissioning, Mr Adams said the IRA and other paramilitaries had made it clear weapons would not be surrendered. Sinn Fein was not an armed group and decommissioning must not be used to subvert the rights of the party's electorate.
Meanwhile, the former European Commissioner and Irish attorney general, Mr Peter Sutherland, visited Belfast yesterday to express support for the Yes campaign.
Accompanied by the SDLP leader, Mr John Hume, he argued that from an economic perspective a Yes vote would be very beneficial for Northern Ireland. Mr Sutherland, who is chairman of British Petroleum, said a peaceful environment would lead to a sustainably prosperous Northern Ireland whose economy would grow rapidly.
Mr Hume said those in favour of the No vote were campaigning for people not to live together in agreement.
"Here for the first time in our history we have an agreement whereby both sections of the community will be working together. Both sections of the community will be fully respecting one another. No one section will be seeking to defeat the other. Think of the strength of that. And what's the alternative? No. No what? No everything."
Other groups to issue statements in favour of the agreement yesterday were: Workers' Party Youth, Democratic Left, the Green Party, the Peace Train organisation, the two Labour groupings in the North, the New Ireland Group and the Women's Coalition.
