Lance Armstrong's return to competitive sport this weekend will be against veteran swimmers, a Texas newspaper reported.
Most competitors in the US Masters Swimming event entered by Armstrong will be older than the 41-year-old cyclist, the Austin American-Statesman said.
Armstrong is banned for life from all competitions that adhere to world anti-doping codes, but is allowed to take part in the low-profile Austin swimming event.
US Masters Swimming executive director Rob Butcher said nobody had raised formal objections to Armstrong competing.
Butcher added: "The purpose of our organisation is to encourage adults to swim."
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Find out what to expect from the weather if you are running in the big race in London or watching from the sidelines.
It will be a soggy start to the weekend and temperatures will drop making it feel colder than in recent days.