Michael Phelps has the chance to add one more medal to his tally on the final day of swimming at the London Games.
The American swimmer won the men's 100 metres butterfly gold medal on Friday, taking his tally of gold medals to 21.
He came from seventh at the turn to win. in a time of 51.21 seconds.
The win took his career tally to 21 medals over three Games, making him the most decorated Olympian.
Phelps still has one more race before he hangs up his goggles, the men's 4x100 medley relay, where he is expected to swim the butterfly leg.
The Americans have dominated in the pool, winning 14 golds this week, 10 more than any other country.
