The US ambassador to Ireland, Mr Richard J.Egan, has unexpectedly submitted his resignation after just 15 months in the post.
He will continue to serve into the new year, with his date of departure determined by President Bush.
A spokeswoman for the embassy last night confirmed that Mr Egan had decided to submit his resignation. Mr Egan "considered it a high honour to serve as ambassador to Ireland". She gave no reason for the move, although it is believed the ambassador has decided to go for personal reasons.
Diplomatic sources said last night there was no question of his having been asked to leave the post.
It will take some time to choose a successor, even if President Bush formally accepts the resignation quickly and moves to nominate a successor. The confirmation process involving hearings by the US Senate Foreign Relations Committee can be lengthy.
The 66-year-old ambassador presented his credentials to the President on September 10th, 2001. A billionaire co-founder of the data-storage company EMC Corporation, Mr Egan has been a long-standing contributor to the Republican Party. He gave some $338,000 during the 1999-2000 campaign to the party and its candidates and $100,000 to the Bush-Cheney Inaugural Committee.
He did not have political or diplomatic experience but had strong business links with Ireland. During his short tenure he did not make the same impact as his immediate predecessors, Mr Mike Sullivan and Ms Jean Kennedy Smith.
Mr Egan was born in Milton, Massachusetts, and grew up in Boston. In 1953, following graduation from Boston Technical High School, he joined the US Marine Corps, serving as a helicopter crew chief during the Korean conflict.
He qualified as an engineer in 1956 and worked as a design engineer. In 1963 he began graduate studies at the Massachusetts Institute of Technology and subsequently joined the institute's team that developed the Apollo Guidance Computer. He continued his business career with NASA, Lockheed Aircraft, Cambex Inc and Intel Corporation.
He founded his EMC company in 1979 with six employees. It now employs more than 20,000 worldwide and has manufacturing and design centers in Massachusetts, Colorado, North Carolina, Belgium, Ireland and Israel.
Mr Egan married Maureen Fitzgerald in 1956 and the couple have five children and 11 grandchildren.