Australia dominate Olympic medley relay heats
Australia, propelled by a flying start from backstroker Emily Seebohm, stormed into the final of the women's 4x100 metres medley relay after setting the fastest time in the qualifying heats.
Seebohm, a silver medallist in the individual 100 backstroke final, charged through the first leg in 58.57 seconds, less than half a second outside the world record for the event.
Only the lead-off swimmer in a relay can set an individual world record.
The Australians easily won their heat in a time of three minutes, 55.42 seconds to advance to Saturday's final ahead of Japan, Denmark, the United States, the Netherlands, Britain, China and Russia.
The Australians won the event at the past two Olympics and clinched the gold in the 4x100 freestyle relay in London but face a tough task beating the Americans in the final after they rested all their big guns, including Missy Franklin and Rebecca Soni, from the heats.
"Australia has a great history in relays and we always have so much fun," said Seebohm. "I am looking forward to the final."
Michael Phelps will get the chance to end his incredible Olympic career with yet another gold medal after the United States safely navigated their way into the final of the men's 4x100 metres medley relay.
The Americans set the fastest time in Friday's qualifying heats, despite resting their top four swimmers, including Phelps, and will start Saturday's final as the overwhelming favourites to win the gold.
Nick Thoman, Eric Shanteau, Tyler McGill and Cullen Jones set a combined time of three minutes, 32.65 seconds, to qualify fastest ahead of Britain, Japan and Australia.
Apart from the 1980 Moscow Games, which the U.S. boycotted, the Americans have won the event at every Olympics when it has been held, in a world record time, and have a lethal combination this time.
In addition to the incomparable Phelps, who will swim the butterfly leg, the U.S. team for the final will include Matt Grevers, who won gold in the 100 backstroke, Nathan Adrian, who won gold in the 100 freestyle and Brendan Hansen, bronze medalist in the 100 breaststroke.
"I just wanted to go out and set it up for the guys," Shanteau said.
"We're going to be in the stands waving flags. None of us will be in the final relay so we just wanted to bring it home."
China's Sun Yang posted the fastest time in the heats of the men's 1500 metres freestyle to stay on course to complete the long-distance double at the London Olympics.
Sun won the 400 gold medal on the opening day of competition at the Aquatics Centre and is the overwhelming favourite to win the 1500, the longest and most gruelling race in the pool, after setting the world record at last year's world championships in Shanghai.
Churning through the water with seemingly effortless ease, Sun won his heat in a time of 14 minutes, 43.25 seconds, well outside his world record but nearly more than three seconds faster than anyone else.
Tunisia's Oussama Mellouli, the defending Olympic champion, was second fastest overall, ahead of Canada's Ryan Cochrane and Italy's Gregorio Paltrinieri.
"I had some problems with my shoulder bugging me for the last three years but it seems to be working pretty well this morning," Mellouli said.
"I woke up mentally not 100 per cent. The race went well, I'm feeling pretty confident for tomorrow."
South Korea's Park Tae-Hwan, silver medallist in the 400, qualified sixth as 10 men broke the magical 15-minute barrier.
"I am happy with my time but it's slower than my PB," said Park. "It was an average race."
Sun has been one of the outstanding swimmers in London, winning silver medals in the 200 freestyle and 4x200 relays, in addition to his gold in the 400.
Just six men have completed the Olympic 400-1500 double with Russia's Vladimir Salnikov the last to achieve the feat, 32 years ago, in 1980.