WASHINGTON -- Pittsburgh Steelers owner Dan Rooney arrived in Dublin on Thursday and will begin his new career as U.S. ambassador to Ireland.

Rooney is expected to present his credentials to the Irish president Mary McAleese on Friday. His first official appearance as U.S. ambassador is a luncheon with the American Chamber of Commerce on Friday.

On Wednesday Rooney was sworn in as the U.S. ambassador to Ireland. Secretary of State Hillary Rodham Clinton administered the oath to Rooney at a ceremony in the Treaty Room in the State Department in Washington, D.C.

Clinton called it a proud day for the Rooneys’ and the city he’s called home for so long.

“The heart of today’s celebration is Pittsburgh,” Clinton said.

Rooney -- who will turn 77 in a few weeks -- and his wife will leave for Ireland on Thursday.

“Patricia and I will do everything we can … between Ireland and America,” Rooney said.

Rooney's nomination was approved last week in Washington.

President Barack Obama announced Rooney's nomination to be ambassador in March.

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Rooney was a lifelong Republican who backed Obama over Hillary Rodham Clinton during Pennsylvania's presidential primary last year. He later campaigned for Obama in western Pennsylvania and helped him win the state in November.

Rooney has been an advocate for peace and education programs in the country for years, but he said that moving to Ireland would be a new challenge.

Rooney, who is part Irish, knows Ireland almost as well as he knows Pittsburgh. He and his wife have been traveling there for 40 years.

In 1976, Rooney co-founded the American Ireland Fund, an organization that to date has raised more than $300 million for peace and education programs in Ireland.

He also founded the annual prize for Irish Literature in 1987 and co-founded the Ireland Institution of Pittsburgh in 1989. In 1993, the “Rooney Fellowship” was created to honor his generosity and charitable works.

Rooney's father, Arthur J. Rooney, founded the Steelers in 1933. The son took over the presidency of the team in 1975 and is a Hall of Fame owner. His Steelers won the Super Bowl this year.

The "Rooney Rule," which requires any team with a head coaching vacancy to interview at least one minority candidate, was developed by an NFL committee Rooney chaired. Rooney has also participated in labor negotiations between the league and players.