Senator George Mitchell has said he firmly believes that decommissioning will happen and he has told anti-agreement unionists that if the current deal fails there will be no arms handover.
Offering his support for the Ulster Unionist leader, Mr David Trimble, Senator Mitchell said: "There has been a lot of talk about guarantees. There is one guarantee. It is that if this process fails there will be no chance whatsoever for any decommissioning.
"If I may use a phrase I had never even heard of until I came to Northern Ireland: even the dogs in the street know there will be no decommissioning, no possibility of decommissioning, if Mr Trimble is rejected and if this process fails."
He said even Mr Trimble's critics did not argue that their course of action would produce decommissioning.
"They know it won't, as does everybody else. So it seems to me Mr Trimble, Mr Adams, Mr Hume and all the party leaders have widely and correctly concluded that if you really want decommissioning as opposed to just talking about decommissioning, this is the best way of achieving it, and I believe that it will happen."
Senator Mitchell said what was different now from when be first became involved in Northern Ireland was that apart from a tiny minority on the fringes of both communities, the overwhelming majority of people wanted devolution and decommissioning.
People wanted conflict to be in the past and genuine peace and reconciliation. The leaders of the pro-agreement parties were attempting to carry out the will of society. Senator Mitchell praised the "wisdom and courage" of the political leaders to do what was right.
He admitted he had suffered frustration, disappointment and worry during the process, but never despair or hopelessness.
He predicted that on the economic front there could be "an enormous peace dividend" for the North. The absence of stable government and peace had been a severe deterrent to investors in the US and elsewhere.
He said his review of the implementation of the Belfast Agreement had transformed relations between the UUP and Sinn Fein from harsh and cold to more trusting.
He praised all involved for having set aside their hostility for the good of their society.
He wanted to see a society "in which hope and opportunity are alive and where a durable peace, tolerance and mutual respect are not distant dreams but rather the reality of daily life for all the people."