The President, Mrs Mary McAleese, is among the thousands of mourners expected to attend a funeral service for former US leader Ronald Reagan today.
Many past and present world leaders are in Washington for a funeral service today at the National Cathedral. They included former British prime minister Margaret Thatcher and former Soviet leader Mr Mikhail Gorbachev.
US President George W. Bush yesterday joined tens of thousands of people filing silently by Reagan's body at the US Capitol in Washington.
At least 2,000 people an hour filed past the coffin in the Capitol Rotunda, some of them after waiting seven hours.
Mr Reagan died on Saturday after a long struggle with Alzheimer's disease. He bade farewell to the American people in a moving letter ten years ago and had since lived in seclusion, cared for by his wife, Nancy.
After the funeral, Reagan's body will be flown back to California one last time for a sunset burial today on the grounds of his presidential library overlooking desert hills just north of Los Angeles.
Since his death, the US media have provided blanket coverage and glowing assessments of the historical legacy and sunny personality of a man rated by some as one of the most significant US presidents of the 20th century.
Little mention has been made of the fact that Reagan was often seen as a sharply divisive figure during his eight years in office between 1981 and 1989.