The United States medal machine finally rumbled into gear at the Shanghai world championships, as Olympic hero Michael Phelps got to work in pursuit of another trophy haul in China. Six days after competition started in Shanghai, the USA bagged their first medal of the championships with victory in the 5km team swim, an event not raced at the worlds since 1998. Andrew Gemmell, Sean Ryan and Ashley Twichell completed the Jinshan City Beach course in 57min 0.6sec, more than a second ahead of the Australian team with Germany taking bronze. The win places the United States equal fourth on the medals table alongside Britain and behind hosts China, Russia and Greece. Most of the 13 golds handed out so far have been for diving and synchronised swimming. But America will be expected to dominate the second week of competition when their swim stars led by 14-time Olympic champion Phelps take to the newly built Sea Crown indoor pool. Phelps, returning to China after his record-breaking eight-title haul at the Beijing Olympics, touched down in Shanghai on Wednesday after a training camp in eastern Australia. The 26-year-old superstar could swim up to seven events as he looks to kick-start his London 2012 build-up after a bumpy season in which he has lost three times in the 200m butterfly, ending a nine-year winning streak. \"This is going to be the start for (the Olympics) next year and I think it\'s something that I\'m ready for and something I\'m looking forward to,\" he said last week. Swimming is in need of positive headlines after a high-profile doping case involving Brazilian star Cesar Cielo, who faced a six-hour Court of Arbitration for Sport tribunal in Shanghai on Wednesday. The Olympic and double world champion is now waiting to learn whether he will be suspended for testing positive for a banned diuretic -- a development that could ruin his London 2012 chances. The 5km team swim was returning to the world championships for the first time since 1998. Thomas Lurz, three-time defending champion in the individual event, was among the German swimmers who finished third. \"To win silver in a team event like this is a fantastic feeling,\" said Australia\'s Rhys Mainstone. \"Now I know how the pool swimmers feel when they represent Australia in a relay. Today was awesome.\"