Taoiseach Bertie Ahern is to address the Joint Houses of the US Congress on 30 April, becoming only the fifth person to have addressed joint sessions of Congress and the British Parliament.
Speaking to RTÉ News, Mr Ahern said the invitation was a great honour for Ireland that shows the special relationship between this country and the US.
He also reiterated that he would co-operate with the Mahon Tribunal, saying he hoped there would be fair procedures 'at least some of the time, if not much of the time'.
The last Taoiseach to address the joint houses of Congress was John Bruton in 1996, following on from Liam Cosgrave and Garret FitzGerald.
While two Fianna Fáil presidents - Sean T O'Kelly and Eamon de Valera - also addressed joint sessions, Mr Ahern will be the first serving Taoiseach from Fianna Fáil to do so.
The Washington speech in April follows on from last year's speech to the joint Houses of Parliament at Westminster.
Mr Ahern shares the distinction of addressing Westminister and Congress with Charles de Gaulle, Francois Mitterand, Haile Selasie, and Nelson Mandela.
Click here to watch a full-length interview with the Taoiseach
