A US government official with experience on nuclear disarmament is replace President George W. Bush's special envoy to Ireland, Dr Richard Haass.
Mitchell B Reiss, who replaced Dr Haass as Director of Policy Planning at the State Department, is to take up the post early in the New Year.
It is understood he will not retain the `Special Envoy' status.
Dr Reiss has a long history of working in the field of international affairs and arms control.
He has spent time working with the North Korean government on nuclear disarmament, and is now set to focus on the issue of IRA decommissioning, according to reports.
Sinn Fein's chief negotiator Mr Martin McGuinness welcomed the Bush administration's appointment of Mr Reiss.
``The decision to appoint a new Special Envoy to Ireland is a signal of ongoing commitment by the US Administration to the Irish peace process,'' the Mid Ulster MP said.
``Ambassador Haass did play a positive role during his term and I wish him well in the future.
``I would like to congratulate Mr Reiss on his appointment and Sinn Fein president Gerry Adams has already written to him. Sinn Fein look forward to meeting with Mr Reiss at the earliest opportunity.''