SYDNEY - Ever the optimist, the man whose family surname adorns the title of one of America's biggest business magazines says there won't be a double dip recession in the United States.

And as if the global financial crisis never happened, Forbes Media chairman Stephen Forbes says the economic "turmoil" gripping America is setting the scene for a return to boom times - just like the 1990s.

"It is always messy, always turbulent ... but the kind of turmoil you see is setting the stage for a fantastic recovery."

He was speaking at a conference in Sydney of 400 high-powered chief executives from around the world.

Not surprisingly, the conference, Full Sail Ahead, was in an optimistic mood about the world economy.

And while billionaire US investor Ken Fisher told the conference the US could expect a coming decade of prosperity, its lead as the world's biggest economy would be whittled away.

Fisher said the "disorganised" and "chaotic" emerging nations were firmly in the driver's seat of the world economy, leaving the US to play second fiddle.

"The US is going to be big and important, but it is secondary, it is no longer what it once was."

Fisher said he was bullish about the future, unlike five out of six US investors who "believe we are going sideways or going down".

However, W.L. Ross chief executive Wilbur Ross jnr sounded a cautionary note, saying the global financial crisis was unlike previous recessions because debt levels among governments and consumers were higher than before.