Mr John Hume, who announced on Monday that he is stepping down as SDLP leader, has said he will continue to act as a public representative, "particularly at European and international level".
Mr Hume is resigning because of health problems. Praising the loyalty of party colleagues and supporters, Mr Hume said on Monday that the decision to resign had been a difficult one: "The SDLP has been virtually my lifetime's work since 1969, when I was involved in setting up this party."
He denied he had come under pressure from the party to retire.
At a press conference to announce his resignation, Mr Hume urged action by republicans on decommissioning of paramilitary weapons.
"Given the current international atmosphere, could I say directly to Sinn Fein: `Please do all that you have to do, and all that you actually can do . . . by taking the necessary action to ensure that all weapons are put completely beyond use, and do so to the satisfaction of the international commission.' "
Mr Hume said it was crucial that the momentum of the peace process be maintained: "The principles at the heart of the Good Friday agreement can offer hope to any area of conflict in the world, and that strengthens the duty of our parties to take the necessary steps to implement it in full."
In the light of last week's attacks in America, he said, all democratic countries should work together to defeat terrorism "but do so in a manner that concentrates on dealing with the actual people and organisations involved in the terrorism and not to take any action which puts at risk the lives of innocent people".
Mr Hume said he was proud of having been leader of a party that was committed to creating peace and stability in Ireland. "Central to our whole approach throughout the troubled years was our total and absolute opposition to violence," he said.