Senior Northern Ireland politicians have sent good wishes to former US senator George Mitchell, a peace envoy in Northern Ireland in the 1990s, after it emerged he had started treatment for leukaemia.
Mr Mitchell (87) is being treated at the Dana-Farber Cancer Institute in Boston.
The former Senator brokered the historic 1998 Good Friday Agreement in Northern Ireland and was awarded the USA's Presidential Medal of Freedom in 1999.
Last night Ulster Unionist Lord Reg Empey, who worked closely with the Senator during the negotiations which led to the Belfast Agreement in 1998, said: "I was very sorry to hear that George Mitchell has been admitted to hospital for cancer treatment.
"It was only a few days ago that he was on the radio speaking of his admiration for the late John Hume so I had no idea that he was unwell.
"The people of Northern Ireland owe George a great deal for the sterling work he did in presiding over the talks that led to the Belfast Agreement.
"Having worked closely with him for over two long years, I know that his patience, determination and balanced Chairmanship of the Talks were critical in leading to success.
"I hope and pray that he will have a speedy recovery," he added.
Former SDLP leader Margaret Ritchie, now Baroness Ritchie, said people all across the island of Ireland would be thinking about Senator Mitchell and wishing him a speedy recovery.
"I want to wish him the best for a speedy recovery from whatever treatment he is undergoing for his leukaemia," she told the Belfast Telegraph.
"Every good wish goes out to him for his treatment programme and a full recovery.
"The community in Northern Ireland and on the island of Ireland will want to let him know their thoughts and support are with him in his illness."
Senator Mitchell was also a former Chancellor of Queen's University Belfast, which hosts a research institute named after him.
Present SDLP leader Colum Eastwood said: "My thoughts and prayers are with Senator Mitchell and his family as he begins treatment.
"His efforts to secure a lasting peace agreement in Northern Ireland have ensured that a new generation grows up free to pursue their ambitions free from the threat of violence.
"I know that people across these islands will be wishing him and his family well."
He was also a peace envoy in the Middle East, focused on the Palestinian-Israeli conflict during President Barack Obama's administration, and is a consultant and former chairman of the global law firm DLA Piper.
Mr Mitchell was also selected by Major League Baseball to investigate steroid use by players, leading to the eponymous Mitchell Report.
Mr Mitchell won election twice as a US Democrat senator, and served as majority leader after first being appointed to fill a position left vacant when the late Edmund Muskie was chosen to serve as secretary of state under President Jimmy Carter.
Before that, he served as a US attorney and federal judge.
Mr Mitchell was previously diagnosed with what was termed "small, low-grade and localised" prostate cancer in 2007.