Taoiseach Bertie Ahern tonight left for the United States as he prepares for one of his last and most prestigious official engagements.
Mr Ahern will address a Joint Session of the US Congress in Washington, less than a week before he stands down from office.
Last year he addressed the British Parliament in Westminster, and with the Congress speech he joins an elite group of five international statesmen to be invited to speak at both houses.
He follows in the footsteps of former South African President Nelson Mandela, Ethiopia's last Emperor Haile Selassie and French leaders Charles de Gaulle and Francois Mitterand.
Mr Ahern was the first Irish leader to address MPs at Westminster.
Accepting the invitation to Congress from Speaker of the House of Representatives Nancy Pelosi in February, Mr Ahern said he had been deeply honoured.
After his final national address to Fianna Fail in Dublin on Sunday, Mr Ahern revealed his speech on Capitol Hill would differ from his address to MPs in Westminster.
He added that rather than look at history he would concentrate on the present, with issues of mutual concern and the strong economic, cultural and social links between Ireland and the US likely to feature.
After his speech Mr Ahern will meet President George Bush in the White House, the second time the leaders have met this year following St Patrick's Day talks in March.