The Northern Secretary, Mr Peter Mandelson, has expressed his "deep personal gratitude" to Senator George Mitchell for "all he has done and all he has achieved".
Speaking after a Cabinet meeting in London, Mr Mandelson said Mr Mitchell had devoted four years of his life to building up the Northern Ireland peace process.
"George Mitchell has helped transform the situation from one of conflict and confrontation to dialogue and peace," he said. "We are forever in his debt."
The Irish Congress of Trade Unions strongly welcomed what it described as a "very significant move" towards the establishment of new political institutions, decommissioning and the implementation of the Good Friday agreement.
The ICTU president, Ms Inez McCormack, congratulated political leaders, particularly the UUP leader, Mr David Trimble and the Sinn Fein president, Mr Gerry Adams.
Anti-agreement parties were quick to condemn the Mitchell review's outcome and in particular the role of Mr Trimble.
The United Unionist Assembly Party, led by the Orange Order Grand Master, Mr Denis Watson, appealed to all "right-thinking" Ulster Unionists to "remain steadfast in upholding the current party policy."
The Northern Ireland Unionist Party said the Mitchell review had secured the "ultimate triumph" of Irish republicanism. It called on dissidents within the UUP to "move decisively and take control" of the party.
The president of Republican Sinn Fein, Mr Ruairi O Bradaigh, said the deal negotiated by Senator Mitchell was aimed at appeasing unionists and fudged the question of decommissioning.