A delighted President Clinton has issued two statements welcoming the approval of the Northern Ireland peace accord and has telephoned his congratulations to the Taoiseach, Mr Ahern, and party leaders.
The result has been given widespread coverage in the US media, which has welcomed it as the most significant development in the search for a permanent solution to the Northern Ireland problem in the past 70 years.
However, editorial writers also caution that the opponents of the accord will try to undermine the workings of the future assembly.
President Clinton hailed the result as "a beacon to peoples around the globe in places where strife prevails and peace seems remote. You have set an example for the world and established a strong foundation for peace," he said when congratulating the people of Northern Ireland and the Republic of Ireland "for seizing this unique opportunity for a lasting peace".
"I pledge that my administration will work with Northern Ireland's leaders as they seek to transform the promise of the accord into a reality with new democratic institutions and new economic opportunities for all of Northern Ireland's people.
"Working through the International Fund for Ireland and the private sector, we will help the people seize the opportunities that peace will bring to attract new investment to create new factories, workplaces and jobs and establish new centres of learning to prepare for the 21st century."
Later on Saturday, in a more informal message, President Clinton described the result as "the culmination of a springtime of peace and it must be the beginning of a long season of happiness and prosperity".
He added: "I salute the leaders who stood for hope against fear, the future against the past, unity against division. Most of all, I congratulate the Irish people for having the courage and wisdom to vote for a brighter future for their children.
"As of today, peace is no longer a dream, it is a reality. You have indeed joined hope to history. All over America, the eyes of Irish-Americans and indeed all our peaceloving citizens are smiling. We are very proud of you."
The President's messages were read out to Irish-Americans celebrating in Washington by the Irish ambassador, Mr Sean O hUiginn, and the deputy British ambassador, Mr Anthony Cary. The Washington Friends of Ireland association had organised a brunch at the Four Provinces on Connecticut Avenue.
Mr Larry Butler, a White House adviser to President Clinton on Northern Ireland matters, also addressed the gathering on the President's delight at the result of the referendums.
Senator Edward Kennedy in a statement said the outcome was "a resounding victory that brings the reality of peace significantly closer for all the people of Ireland, North and South".
While "there will be difficulties ahead", the "Protestant and Catholic leaders who had the courage to break with the violent past and negotiate this historic opportunity now have an emphatic mandate from their long-suffering constituents to make this agreement work and fulfil its promise of peace."
Mr Ben Gilman, chairman of the House International Relations Committee on Capitol Hill, said he intended early next year to hold "full committee hearings on the implementation of the Good Friday Belfast accord, especially on the much-needed changes and reform of the RUC".
The New York Times, in an editorial, said: "It will take years to construct a permanent peace, but the vote can be a vital downpayment." It added: "Some Protestant opponents of the peace agreement hope to win election to the assembly to scuttle the North-South body. These saboteurs would be betraying the cause they hold most dear, majority rule."