Senator George Mitchell has said that unionists who criticised the leadership of Mr David Trimble should now recognise that his tactics have secured Provisional IRA disarmament.
Mr Mitchell, who chaired the lengthy political talks which led to the signing of the Belfast Agreement, yesterday said the UUP leader should be given due credit as he attempts to be restored to the office of First Minister.
"I would hope that all of those on the unionist side who have been critical of David Trimble's leadership will now recognise that he has been right all along," he said.
Mr Mitchell, who was speaking on the BBC's Breakfast With Frost, insisted the significance of the IRA's gesture on disarmament must be recognised.
Praising the risks Mr Trimble has taken for the peace process, he said: "He has been quite courageous in taking these steps as have the other political leaders who are part of the pro-agreement effort."
He said all paramilitary organisations in the North would have to put their weapons beyond use.
Meanwhile President Bush's special envoy to the North, Mr Richard Haass, has said the September 11th attack on the US played a significant role in helping to bring about IRA decommissioning.
Speaking yesterday on BBC Radio Four's World This Weekend, he said: "What September 11 did was bring about a sea-change in American thinking. There is simply zero tolerance in this country for terrorism of any sort anywhere. When the leaders of Sinn FΘin and the IRA saw this, and saw their traditional sources of support in the US would very likely be affected, I think that, in turn, caused them to reconsider their own long-standing policy."