The international Irish dance association has decided to bring its 2009 world championships to Philadelphia, marking the first time the annual event will be held outside the British Isles.

The gathering is expected to bring up to 20,000 dancers and their relatives, teachers and friends to the city during Easter Week, usually a slow period for conventions.

The decision by Dublin-based An Coimisiun le Rinci Gaelacha (the Irish Dance Commission) to hold its world championships in the city comes as 2,200 Irish dancers and their families are scheduled to gather in Philadelphia this Thanksgiving weekend for the annual Mid-Atlantic Championships at the Center City Marriott Hotel.

It also underscores the international reach of Irish dance, popularized in recent years by the Riverdance stage productions.

Seamus O'Se (pronounced O'Shea), the commission's chairman, said a big selling point in Philadelphia's bid to host the competition was the proposed venue: the Kimmel Center.

"We don't have the Kimmel Center in Ireland, or its likes, either," O'Se said in a telephone interview from Atlanta.

Boston also made a bid for the event.

O'Se said dancers will come from Ireland, Scotland, England, Wales, Europe, Australia, New Zealand, South Africa and Canada as well as the United States to compete in the championships.

Jack Ferguson, executive vice president for sales for the Philadelphia Convention and Visitors Bureau, who made the pitch for the city in Ireland, said, "You could hear the oohs and the aahs" when the Kimmel Center was brought up.

"For what they're doing, [the Kimmel] is purpose-built," he said. "I think it will have high visibility for the city... . It's a tremendous win."

The world championships started "very humbly" in Dublin in 1970 with about 500 people in the theater, O'Se said.

Since then, all the championships have been held in Ireland and Scotland.

O'Se said the decision to take the event to the United States would not be without some controversy.

"There is a certain traditionalist element who feel, 'Oh, God, it's going across the Atlantic now and it will never come back,' " he said. "Overall, we've become very international... but I don't think any of these kinds of fears are well founded.

"As matter of fact," he added, "a lot of the U.S. people love coming to Ireland for the event. They don't even like going to Scotland. They want it in Ireland."

Debbie Lynch-Webber, the chair of the mid-Atlantic championships, said it was "wonderful" that the world competition was coming to Philadelphia.

She said a weak dollar made it very costly to attend the championships in Ireland and Scotland.