Northern Ireland's political leaders have paid tribute to Senator Edward Kennedy, the Democratic senator from Massachusetts, who has died aged 77.
Mr Kennedy was nominated for a knighthood earlier this year for "services to the British-American relationship and to Northern Ireland".
Secretary of State Shaun Woodward said he was "an immense figure."
Deputy First Minister Martin McGuinness said despite disagreements he had "always respected" the senator.
Mr McGuinness added, ""I always found him during the course of the peace process, whatever about his views on Irish republicanism and on the the conflict and on the IRA prior to 1994, he certainly was hugely supportive."
In December 2007 Senator Kennedy met Ian Paisley and Martin McGuinness during the first and deputy first ministers' visit to the US.
In 2006, he paid tribute to the family of murder victim Robert McCartney after meeting them in Washington.
Senator Kennedy described the McCartney murder as a "defining issue" and paid tribute to the women of the family who had "persevered in the face of intimidation and harassment".
During the Troubles, the senator played a leading role in America in supporting nationalists in Northern Ireland and was often a controversial figure to unionists.
The vast, vast majority of Irish Catholics in America bear you no ill will. We are brothers and sisters, not enemies
He made an emotional journey to Ireland in 1970 and was soon embroiled in calls for the British Army to move out of Northern Ireland.
Mr Kennedy was one of four influential Irish-American politicians - known as the four horsemen - with whom former SDLP leader John Hume forged a strong relationship.
He helped garner support for Mr Hume's belief in peaceful, gradual change bolstered by economic development.
After the IRA ceasefire in 1994, he demanded that London move on talks with Sinn Féin. He met Sinn Féin leader Gerry Adams and other politicians during and beyond the Good Friday Agreement.
Despite his strong interest in Northern Ireland, it was not until 1998 that he first visited there.
Martin McGuinness: "He was hugely important to the peace process"
In a speech at Londonderry's Guildhall, he told Protestants in the audience that they were "part of our heritage and history".
"The vast, vast majority of Irish Catholics in America bear you no ill will. We are brothers and sisters, not enemies," he said.
He praised Northern Ireland's political leaders after the return of power-sharing in May 2007.
Mr Kennedy said: "A brighter day has dawned for the people of Northern Ireland, and it would not have been possible without the commitment and determination by all of Northern Ireland's political leaders to find a new way forward.
"Each of them is a profile in courage for our time and all time."
When proposing Mr Kennedy for a knighthood Prime Minister Gordon Brown said: "Northern Ireland is today at peace, more Americans have health care, more children around the world are going to school and for all those things we owe a great debt to the life and courage of Senator Edward Kennedy."
Senator Kennedy was diagnosed with a malignant brain tumour in May last year.
He became a member of the Senate in 1962 to replace his brother when he resigned to become president, and was re-elected seven times.
The Kennedy family announced his death in a brief statement in the early hours of Wednesday.
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