President Clinton and the British Prime Minister, Mr Tony Blair, yesterday urged people on both sides of the Border to support the Belfast Agreement, saying it would end violence "once and for all".
In a joint appearance with the US President ahead of the Group of Eight (G8) summit in Birmingham, Mr Blair said, "If people are supporting this agreement, they are supporting an end to violence once and for all."
Mr Clinton said this was the "chance of a generation" for peace in Northern Ireland, adding, "We will stand with those who stand for peace, but I want to make it equally clear that anyone who reverts to violence, from whatever side and whatever faction, will have no friends in America."
The US President considered visiting the region next week ahead of Friday's referendum but he said he decided not to because it was not his place to campaign abroad as a foreigner.
"No matter how friendly an outsider I am, I still am an outsider and I won't have to live with this," Mr Clinton said. "It's their decision to make."
British officials said Mr Blair planned a trip to Northern Ireland next week.
"At the heart of this agreement is the belief that we only make progress if people give up violence for good, and we will make sure in legislation that comes before our Parliament . . . that we make that commitment very, very clearly expressed," Mr Blair said.