TOKYO, July 22 (Reuters) - America"s traditional dominance in the pool faces a double threat at the Tokyo Games with a new wave of East European men and Australian women looking to end any chance of a repeat of the U.S. successes in Rio and London. The Americans amassed 16 swimming gold medals in each of the past two Games but with Michael Phelps now watching from the television commentary position, having retired with 23 golds, there is a real sense that the competition, which gets under way with heats on Saturday, could be the most open since the end of the Cold War. Certainly the rankings suggest a broader spread of gold medal winners, but the Americans are hoping their habit of peaking for the Games will see off the various threats. "I think it is going to be phenomenal," says Canada"s High Performance Director John Atkinson. "The challenge with any Olympics is who can be recovered to swim multiple times in nine days. How you sustain performance, how you recover, how you look after yourself, are going to be the key things because not always the fastest swimmer wins," said the British born coach. American hopes in the men"s races are pinned on Caeleb Dressel in the 50 and 100 metres freestyle and 100 butterfly but the medals are likely to be spread around. Russian Anton Chupkov is favourite in the 200m breaststroke and Hungarian Kristof Milak the man to beat in the 200m fly. Remarkably, Team USA has won gold in the men’s 100 and 200 backstroke in the past six Olympic Games but that streak is under real threat in Tokyo with American Ryan Murphy facing a battle to repeat his 2016 successes. Russians Evgeny Rylov and Kliment Kolesnikov are strong contenders in a very deep field in the 100 backstroke while in the 200, world champion Rylov is again well placed and Britain"s Luke Greenbank is also in the frame. Greenbank"s compatriot Adam Peaty is strong favourite in the 100m breaststroke having recorded the 16 fastest times in the event while another Briton, Duncan Scott, has a strong chance in the 200m free. HOME GLORY There may be no fans in the arena but there could be home glory in the 400m individual medley with Japan"s Daiya Seto going head-to-head with American Chase Kalisz. In the women"s races, American Lilly King"s confident claim that the U.S could win all the individual medals would require a series of surprises. The U.S. are ranked number one in only five of the 14 races with Australia in top spot in seven. Five-times gold medallist Katie Ledecky, who hopes to become the most successful female Olympic swimmer of all time, faces a real challenge from Australian Ariarne Titmus in the 200m and 400m freestyle that she triumphed in at Rio. The Australians are confident of a memorable games from a powerful squad with Cate Campbell looking for gold in the 50 and 100m free and Kaylee McKeown the favourite in the 100 and 200 backstroke. But the Aussies know that, while the rankings suggest it could be a golden week in the pool, their rivals have a habit of delivering when it matters. "The Americans have proven historically, at the Olympics that they perform. So for us, you know they"re the standard that were striving for. And they rightly so have deserved that," Australia head coach Rohan Taylor said on Thursday. "On paper it looks like we are (looking good), but you know when you come to this competition, it"s about who has the competitive IQ to perform under pressure, the American system breeds competitive athletes, their whole college system, the best competitive people come out of the top. "But we believe this year, I think we have some really strong competitive, strong mentally competitive athletes," he added. King will renew battle in the 100m breaststroke with Russian Yulia Efimova, a duel that flared up in Rio when King wagged her finger at the previously suspended Russian and branded her a drug cheat.