US politicians tonight paid tribute to Mr Ahern and to the good relationship he has enjoyed with the White House during his time as Taoiseach.
A White House spokesman said President George Bush "has enjoyed his many meetings and working relationship with the Taoiseach, and wishes him well in his future endeavours".
Hillary Clinton described Mr Ahern as "a great partner of the United States and a dear friend whose career has been one of great accomplishment.
"As First Lady and Senator, I have had the honour to work with him on several occasions. His leadership during the time leading up to the agreement and the 10 years following have resulted in significant progress even when the outlook was unclear," she said.
Senator Edward Kennedy described Mr Ahern as "a steady and effective leader of the Irish people" who had made an indispensable contribution to the resolution of the conflict in Northern Ireland.
New York Republican congressman Peter King described Mr Ahern as an "outstanding Taoiseach" whom he regarded as a friend.