A little more than two weeks ago, White House officials contacted Pittsburgh Mayor Luke Ravenstahl and other officials with two questions: Would they be interested in hosting an international event, and could they keep it a secret?

That set off a frenzy of meetings and calls among government, business, and hotel officials that culminated in yesterday's White House announcement that Pittsburgh would host the Group of 20 economic summit Sept. 24-25 at the David L. Lawrence Convention Center.

The key - besides not letting word leak out before the announcement - was clearing blocks of hotel rooms and making them available at rates that world leaders were willing to pay.

The summit will draw the leaders of the top 20 economic powers, who are responsible for 85 percent of the world's spending. The event follows an April meeting in London; it will serve as an update on the world economic crisis and will highlight the economic benefits of environmentally friendly practices.

Expected at the summit, besides President Obama, are the leaders of Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, the United Kingdom, and the European Union - along with the European Central Bank.

Joseph McGrath, president and CEO of VisitPittsburgh, said his organization was brought in early by the city and Allegheny County to work out the summit logistics.

White House officials "were looking for room blocks, and we had to get the commitments from the hotel operators," he said. "It was a little different because we were not at liberty to tell them what the event was."

White House officials said they focused on Pittsburgh because of the city's economic recovery from the decline of the steel industry in the 1980s, and because of its leadership in environmentally friendly buildings.

Pittsburgh's convention center, which administration officials were familiar with from campaign visits, is the largest LEED-certified center in the world. LEED - the Leadership in Energy and Environmental Design certification system - was developed by the U.S. Green Building Council.

"This is a tremendous opportunity for Pittsburgh," said city Chief of Staff Yarone Zober. "This is a chance for us to showcase our city, and our region, for the world."

Among the selling points: "Pittsburgh has really been a model for an economic turnaround," he said, noting the smokestacks-to-knowledge transformation of the regional economy, and the development of green job sectors.

Zober acknowledged that preparing the city to host the world's leaders would be a big job.

"We're going to make sure that this city shines," he said. "This is potentially one of the largest things to happen in Pittsburgh."

The city's public safety departments have begun coordinating security planning with the Secret Service, he said. The federal government is expected to cover most of the costs associated with hosting the summit.

Gov. Rendell, in a statement, said he was honored by the city's selection. "Any doubts that Pittsburgh is a world-class city with a bright future should be erased by this choice," he said.