Mo Farah has switched to the 5000m from 10,000m for his opening Diamond League race of the season in Eugene, Oregon.
Farah, who won gold at both distances at the London Olympics, changed events after recently suffering from a stomach virus.
By changing events, it means the 30-year-old will avoid facing world record holder Kenenisa Bekele over the longer distance.
As well as Farah, there are a number of other Britons competing in America, with Christine Ohuruogu and Robbie Grabarz also competing.
Olympic long jump gold medallist Greg Rutherford will also take part in the event but it will be very tricky for him to win the first Diamond League event of the season.
As well as Rutherford, the previous two winners of the Olympic long jump will compete.
Dwight Phillips won in Athens in 2004 while four years later, Irving Saladino won Panama's first ever medal when he topped the podium in Beijing.
London silver medallist Ohuruogu also faces a tough test as the other two medal winners from last year take part in the 400m alongside the Brit - champion Sanya Richards-Ross and DeeDee Trotter of the USA who finished third.
The event runs for two days, starting on Friday.
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