Washington ? Call him Barack O’Bama.

As White House fountains ran green for St. Patrick’s Day, the president saluted strong U.S.-Irish ties in a warm welcome for Ireland’s leaders and turned to a critical campaign backer, Pittsburgh Steelers owner Dan Rooney, to fill the post of U.S. ambassador to Ireland.

And in a wee bit of blarney, Obama boasted of Irish ancestry.

“My great-great-great-grandfather on my mother’s side hailed from a small village in County Offaly,” he said, recalling a genealogical gem from the campaign fitting for a meeting with Ireland’s prime minister, Brian Cowen.

He even joked to Cowen: “We may be cousins. We haven’t sorted that through yet.”

On a serious note, Obama and his aides pushed to salvage a peace in Northern Ireland during private meetings with political leaders. Obama and Cowen met in the Oval Office; the president held a separate session with Northern Ireland’s First Minister Peter Robinson and his deputy, Martin McGuinness.

Earlier this month, two soldiers were fatally shot and a policeman murdered two days later.