Michael Phelps has opted out of the 200m freestyle at the Olympic Games and will instead chase seven gold medals.
The American is expected to concentrate on two butterfly and two individual medley events as well as three relays.
His coach Bob Bowman said Phelps was "removing the individual 200m freestyle from his Olympic programme. This will give him a full slate of seven events."
Phelps is the most successful Olympian ever, having won a total of 14 golds, including eight in Beijing in 2008.
"It makes sense - no-one should be expected to do that twice," tweeted Bowman. "Once was enough."
"This change will allow him to focus more energy on relays for Team USA."
Phelps had seemed ready to compete in eight events after he won three at the US trials.
But although he won the 200m freestyle in Beijing four years ago, he has since been beaten over that distance in the last two World Championships.
US head coach Gregg Troy said Ricky Berens, who finished third in the 200m freestyle at the trials, would replace Phelps in London.
"It was a fun week but there are still a lot of things that need to be perfected," said Phelps after the trials.
"It shows that I can do it in a programme at a high level again. I was struggling over the last few years."
He has won a total of 38 world and Olympic gold medals in his career but admitted he struggled for motivation after Beijing 2008.
He has also faced increasing competition from fellow American Ryan Lochte, who will now be favourite for the 200m freestyle after Phelps's withdrawal.
At last year's World Championships in Shanghai, Lochte, 27, won five titles, one more than Phelps, who is also 27.
The Phelps and Lochte rivalry is expected to be one of highlights of the Games, which begin later this month.
"Neither one of us wants to lose," said Phelps. "When we get in the water we race as hard as we can, whether we're playing cat and mouse by the end, we're going all out.
"They're fun, exciting races and Ryan has proved he's been the best over the past couple of years."
Lochte sounded a warning to Phelps after the trials. "I'm used to racing against him, I've been doing it for eight years now," he said.
"In the past four years, I've gone a lot faster and I know what my body can handle. This meet was just stepping stones for what I really want to do in London."
Lochte, who does not normally compete in the 100m butterfly, missed out on Olympic qualification after Phelps caught Tyler McGill to win in 51.14 seconds - the world's fastest time this year.
McGill took the second Olympic spot in 51.32secs, with Lochte close behind in 51.65secs.
Phelps finished first in the 200m individual medley final and the 200m freestyle final earlier in the trials, while Lochte beat him in the 400m individual medley final and also won the 200m backstroke final.
Missy Franklin, 17, is set to become the first US woman to swim in seven events at the Games after she won the 200m backstroke in 2:06.12.
"I felt really strong. It really hurts so bad at the end but if it doesn't then you're not doing it right," she said.
"I can't believe I have seven events. It's so overwhelming but so exciting at the same time."