The International Olympic Committee says up to 17 countries have expressed interest in hosting future Youth Olympics, including the United States and others from Africa and Latin America.
The inaugural youth winter games will be held in Innsbruck, Austria, in 2012 and the summer games in Nanjing, China in 2014. Lillehammer, Norway, which hosted the 1994 Winter Olympics, is the only city that has expressed an interest in hosting the 2016 winter games, and has until November to submit a formal bid, the IOC said.
The IOC's Olympic Games Executive Director Gilbert Felli said Saturday that an African and Latin American country as well as "some cities in the United States" have expressed interest in hosting the event in 2018 and beyond, but would not name them.
"We have had discussions with the USOC (U.S. Olympic Committee) and some cities in the U.S. who have the idea for the winter or summer games," Felli said. "One day, they would like to come with a bid."
IOC spokesman Mark Adams said the IOC is emphasizing the use of existing facilities to make the youth event more attractive to cities with smaller budgets.
"It gives them a chance to participate, to take part in the whole Olympic ideal," Adams said. "That is why there is interest from cities which would probably never have thought of getting involved and could never see themselves as serious contenders for staging an Olympic event."
IOC President Jacques Rogge praised the Singapore games as it reached the halfway point of the 12-day event. Education programs, including talks with elite athletes, have been popular with the youngsters. Fans have taken to the new sports like 3-on-3 basketball.
"So far everything is going smoothly and we've been very pleased with the organization, the competition and the non-sport activities," Rogge said in a statement. "While it is impossible to provide a full assessment of the games until after they're over, so far we are very satisfied."
American athletes had their best day of the games Saturday, winning two golds, a silver and a bronze.
China leads the games with 20 golds and 33 medals overall. Russia is second with 15 golds and 32 overall, while South Korea has seven golds.
Tang Yi of China has been the star of the games so far. The 17-year-old has won six of her country's 11 swimming golds.
The IOC said the popularity of the games is reaching well beyond Singapore. The Youth Olympics' YouTube channel, part of a broad social media campaign, has had 2.8 million hits. That's higher than the traffic for the 2010 Vancouver Games. The Youth Olympics has 3,500 followers on Twitter and a popular Facebook page.
Organizers from Innsbruck, who plan to host the 2012 winter Youth Olympic with 1,050 athletes from 70 countries, said the Singapore games have given them confidence.
"It's taken some pressure off us because now we know it can work," said Peter Bayer, chief executive of Innsbruck 2012.
Felli said the IOC had concerns that many venues this week were far from full — despite all tickets having been sold.
"You have some sessions where people are coming in the morning and watching for a while and then leaving and they don't come for the afternoon and evening session. That is something of a disappointment," Felli said. "But it was much fuller last night than the beginning of the week, so they are working on that to bring more people in."
In other events, Odane Skeen of Jamaica ran 10.42 seconds to win the boys' 100 gold Saturday, beating Masaki Nashimoto of Japan and David Bolarinwa of Britain. Josephine Omaka of Nigeria won the girls' 100 gold ahead of Myasia Jacobs of the United States and Fany Chalas of the Dominican Republic.
Ekaterina Bleskina of Russia beat out Michelle Jenneke of Australia to win the gold in the 100-meter hurdles while Luguelin Santos of the Dominican Republic took gold in the 400 meters, ahead of Ruan Greyling of South Africa.
In archery, Ibrahim Sabry of Egypt took gold in junior individual category, easily defeating Rick Van Den Oever of the Netherlands. Medals are also scheduled to be handed out in artistic gymnastics, athletics, diving, judo, modern pentathlon and tennis.
The inaugural Youth Olympics in Singapore involves 3,600 athletes ages 14 to 18 from 204 national Olympic committees competing in 26 sports.
Associated Press Writer Alex Kennedy in Singapore contributed to this report.