Mr Bush has urged all communities in Northern Ireland to seize the opportunity for peace presented by the British and Irish government blueprint for the restoration of the North's Executive.
At a joint press conference at Hillsborough, Mr Bush said: "In Northern Ireland, the Prime Minister and I are committed to helping the parties to take the final steps towards a lasting peace."
Referring to the plan, due to be unveiled later in the week by Mr Blair and Taoiseach, Mr Ahern, Mr Bush said: "I support, and my government strongly supports, their efforts. At a meeting this afternoon I will urge Northern Ireland's political leaders to adopt this plan as their own."
"This is an historic moment. May I ask all the communities in Northern Ireland to seize this opportunity for peace," he said.
Mr Bush, Mr Blair and Mr Ahern are due to meet representatives from the SDLP, Sinne Féin and the UUP this afternoon.