Pittsburgh is hoping the world's most powerful leaders will see more than the city's quaint funicular trains and picturesque rivers when they meet here in September.

City leaders hope their selection for the Group of 20 summit signals recognition that in difficult economic times the city has turned from a suffering steel-making centre into a modern hub of education, medicine and technology.

"Our economy is one that's being looked at worldwide, because of our ability to renew ourselves," said Joanna Doven, spokesperson for Mayor Luke Ravenstahl. "The G20 coming to Pittsburgh makes it official - Pittsburgh is back on top."

Announcing the selection of Pittsburgh to host the two-day summit, White House press secretary Robert Gibbs said President Barack Obama wanted to highlight its accomplishments.

"It's an area that has seen its share of economic woes in the past, but because of foresight and investment is now renewed, giving birth to renewed industries that are creating the jobs of the future," Gibbs said at a May 28 briefing.

When in Pittsburgh, world leaders will continue to coordinate recovery of the global economy. But an emerging issue to be discussed is the need for a post-crisis "exit strategy" for cutting public deficits being run up by developed nations through huge stimulus packages.

Pittsburgh was rated America's most liveable city in 2007 by Places Rated Almanac, which had given it the same honour in 1985.

Last month, The Economist also bestowed Pittsburgh with the same "most liveable" honour among U.S. cities and, in January, Forbes magazine listed Pittsburgh among the 10 top US cities for job growth this year.

With Mr Obama as host of the G20 summit, Pittsburgh will deploy about 4,000 police officers for the thousands of delegates, journalists and protesters expected to converge on the city for the meeting of leaders, finance ministers and central bank governors on September 24 and 25.

Activists this time plan to demonstrate for a global jobs programme. Some previous G20 protests have turned violent.

The G20 members are: Argentina, Australia, Brazil, Britain, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, the US and the EU.

The city's downtown is situated at the point where the Allegheny and Monongahela rivers meet and form the Ohio River. It is framed by hills with sweeping views.

In the early 20th century, Pittsburgh was home to the giant US Steel Corp., created by Andrew Carnegie from several steelmakers, and produced as much as half of the nation's steel.

The skies and streets were dark and gritty from the smoke of mills and factories.

By the 1960s US steelmakers were burdened with outmoded and inefficient operations, high labour costs and legacy costs associated with unionised labour, and they were losing market share to highly competitive steelmakers in Asia.

Layoffs became common and by the 1970s, US Steel and others began shutting their mills.

Thanks to the efforts of businesses, public-private development partnerships and publicly subsidised downtown redevelopment efforts in place to this day, the city's businesses, neighbourhoods and people adapted.

Engineering and manufacturing company American Bridge was sold four times before its fifth and current owner, the Ing. Family Trust, with the management of a small cadre of veteran AB workers, began to turn the shrunken company around. AB now works on some of the world's most impressive bridge and port projects, including the San Francisco-Oakland Bay Bridge.