Both the Ulster Unionist Party and the SDLP have welcomed President Bush's call for paramilitary decommissioning, made in an interview with the London Times.
The DUP predicted that the President's appeal would fall on deaf ears, while Sinn Fein claimed Mr Bush's position was in line with its own.
Ahead of his European visit, Mr Bush told the newspaper: "There should be no mistake. We believe that the decommissioning part of the Good Friday agreement must be upheld . . . My government stands side by side with the two governments and their two leaders in urging all sides to decommission, to disarm."
The Ulster Unionist MP for Lagan Valley, Mr Jeffrey Donaldson, said Mr Bush's comments were evidence of the increasing isolation of republicans on the weapons issue.
"I very much welcome President Bush's comments on decommissioning," he said.
The SDLP's Minister of Further and Higher Education, Mr Sean Farren, said Mr Bush's support for the peace process was particularly encouraging.
The deputy leader of the DUP, Mr Peter Robinson, said he was sceptical as to the effectiveness of the US President's comments.
"I don't think his comments on decommissioning are all that different to his predecessor, President Clinton," he said.
However, Sinn Fein insisted yesterday that Mr Bush was sharing republicans' analysis that the situation was at a critical stage and that the need to resolve the issue of arms was an essential part of the Belfast Agreement.
The Sinn Fein MLA, Mr Gerry Kelly, said he welcomed the President's pledge to help in advancing the process.
Mr Bush's appeal for IRA decommissioning marked a subtle but significant hardening of the administration's attitude to the issue and to the IRA, adds Patrick Smyth, Washington Correspondent.
However, it is seen as a change which keeps US policy firmly in step with the position of the Irish and British governments, senior sources here said yesterday.
In arguing that the statement did not represent a significant shift, Irish diplomatic sources emphasised that Mr Bush repeatedly referred to the context of the agreement and his desire to work with both governments.
Mr Bush's comments mark him apart from the silence of Congressional leaders on the issue. Their statements have avoided targeting the decommissioning issue alone, while instead, like Sinn Fein, placing it in the context of the full Belfast Agreement package.