Acting in partnership, there were “few limits to the good” that the US and EU could do, said Mr Ahern.
“Energised by a common framework of values and imbued by democratic principles, together we can and we shall be a beacon for economic progress, individual liberty and the dignity of all mankind,” he said.
Mr Ahern was officially greeted at Congress by the Speaker of the House of Representatives, Nancy Pelosi.
Then, shortly after 11am, he was escorted into the chamber of the house by a delegation of senior senators, including the Senate majority leader Harry Reid, former US presidential candidate John Kerry, and prominent Irish-American politicians Chris Dodd and Patrick Leahy. Senator Edward Kennedy was also present.
The chamber was not full for the occasion, with up to a dozen seats left vacant and many others filled by congressional staff or representatives of politicians.
However, Mr Ahern did receive a warm and rapturous welcome from, among others, homeland security secretary Michael Chertoff, who was representing President Bush.
Representatives of the Armed Forces and diplomatic corps were also in attendance, as was former taoiseach and Fine Gael leader John Bruton, now the EU ambassador to Washington.
Among Mr Ahern’s own party were his sister, Kathleen, and daughter, Cecelia, his election agent Chris Wall, constituency colleague Cyprian Brady TD, former Fianna Fáil fundraiser Des Richardson, property developer Sean Dunne and Senator Donie Cassidy.
Foreign Affairs Minister Dermot Ahern and Transport Minister Noel Dempsey represented the Government.
Mr Ahern did not have the ideal preparation for the momentous occasion, having been evacuated from his hotel in Washington in the early hours of yesterday morning because of a fire alarm.
Mr Ahern was awakened by the US Secret Service shortly after 4am local time [9am Irish] and escorted out of the prestigious Mayflower Hotel, but he and other guests were able to return to their rooms within an hour.
Despite the unwelcome event, Mr Ahern appeared unaffected by tiredness as he began his speech in firm fashion, outlining the strong bonds between Ireland and the US before making a direct appeal on behalf of the illegal Irish in America.
With his speech, Mr Ahern became the sixth official Irish leader to address Congress, following President Seán T Ó Ceallaigh in 1959, President Eamon de Valera in 1964, Taoiseach Liam Cosgrave in 1976, Taoiseach Garret FitzGerald in 1984 and Taoiseach John Bruton in 1996.
But like Mr Ó Ceallaigh before him, Mr Ahern pointed out the first Irish leader to address Congress had actually been Charles Stewart Parnell in 1880.
“Whenever we have asked for help, America has always been there for us — a friend in good times and in bad,” said Mr Ahern.
The Taoiseach recalled the terror attacks of September 11, and in particular Fr Mychal Judge, the Irish-American priest who was chaplain of the New York Fire Department and who was killed inside the Twin Towers.
The Taoiseach also spoke of the strides made by the EU, and how “two great Irish-Americans” — presidents Kennedy and Reagan — had stood firm for freedom during the Cold War.
Mr Ahern moved onto the problems of poverty, starvation and disease, countering international terrorism and containing nuclear proliferation.
He said the world’s common humanity was “being tested” in parts of Africa such as Sudan and Chad, where conflict threatened a whole region with chaos and destruction.
Similarly, he said the international community had to succeed in its efforts to end the Israeli-Palestinian conflict.
He cited peace in Northern Ireland as an example of what could be achieved, and paid tribute to the American politicians such as Senator Kennedy who had helped in that process.
“Our children will live in peace. And their children will enjoy the fruits of their inheritance,” said Mr Ahern. “That is the triumph of people and of politics.”