Mrs Clinton, who had spent part of the weekend at Chequers with Tony Blair, the Prime Minister, and his wife Cherie, said she had noticed a sense of hopefulness during her trip to Dublin and Belfast.
"Although the euphoria of [President Clinton's] trip nearly two years ago is not present, there certainly is a hopefulness and perhaps a more pragmatic sense of what it will take to try to bring the parties together," she told around 100 guests, including Virgin chief Richard Branson, Trevor McDonald, the newsreader, and author Salman Rushdie.
It was extraordinary that both parties in Northern Ireland were sitting down and speaking to one another, she added.
"I congratulate the Prime Minister and this Government for all that they have done to further this event. As I have said in Dublin and Belfast, the President will stand with those who take risks for peace."
She said that a date had been set for Mr Blair to visit America, and added she was very much looking forward to his visit.