Winfrey, whose programme is seen 140 countries and boasts a weekly US audience of 46 million, filled an open-air concert venue on Chicago's Lake Michigan waterfront with more than 4,000 people who jumped, shouted and cheered in swirling red, white and blue confetti as the medalists walked through the aisles and took the stage.

'Team USA, you want to make us all stand taller,' she told the athletes at the end of the programme, adding that she hoped they would have a chance to return to Chicago for the 2016 games, for which the city is bidding against Madrid, Rio de Janeiro and Tokyo.

Swimmer Michael Phelps, who came back from last month's games in Beijing with a record eight gold medals, told Winfrey his feat had not sunk in but 'I need to get back home' to Maryland to see friends and his pet bulldog.

'One of the biggest things I want to do is is grow the sport of swimming,' he added, noting that he has established a charitable foundation to promote the sport using the US$1 million (S$1.4 million) bonus he earned from the makers of Speedo swimwear.

Wednesday's show, which will air in syndication on Sept 8, marked the start of Winfrey's 23rd season.

Another swimming star, silver medalist Dara Torres, told Winfrey she was not done with competitive swimming at age 41.

'I kind of want to keep going for a bit,' she said, unlike past Olympic competitions after which, she said, she didn't want to go near the water again.

'When you're in the water the water doesn't know your age,' she added.

The venue for the 2016 games will be announced in October next year. Phelps was scheduled to meet with Chicago community leaders later in the day to help provide support for the city's bid. -- REUTERS