American swimmers going to this summer's Athens Olympics said on Sunday they were not concerned by the prospect of competing at a venue without a roof.

Athens organisers had come under intense criticism in March when construction delays forced builders to scrap plans to cover the swimming venue.

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While spectators can expect to broil in the searing summer sun, American swimmers like 18-year-old Michael Phelps, who will attempt to match Mark Spitz's record of seven gold medals at a single Olympics, are predicting fast times and few problems.

"A pool is a pool," Phelps said. "We're all going to be competing under the same conditions and the swimmers will adapt.

"If a pool has lanes and water that's all you need."

There had been fears that without the protection provided by the steel and glass roof, swimmers would suffer under the elements and force drastic changes to training programmes in the final build-up to the August 13-29 Games.

But for most of the American swimmers, who grew up competing outdoors and will hold their Olympic trials outside next month in California, there is little to fear from the open air conditions.

"I think maybe some of the distance swimmers will be affected the most," said Lindsay Benko.

"The distance swimmers might get a little warm from the sun that would be my only concern."

Still, the outdoor setting will present some unique challenges, particularly for backstrokers who will not have a roof for reference.

"There are a lot of swimmers constantly training indoors so you can judge you're going straight using the roof so for swimmers use to that that might affect them," said Brooke Bennett, who will try to defend her 800m freestyle gold medal in Athens.

"But other than that the pool is going to be fast it's more about the competition and the crowd in my opinion."

"I'm from California and I've trained outdoors my entire life," 100 metre backstroke world record holder Nathalie Coughlin said.

"I'm not too worried about swimming backstroke without a ceiling because I never had a ceiling. It's something I can't control but everyone is going to be under the same conditions.

"I'm pretty use to not having a roof and in 92 they swam well and didn't have a roof there so I'm not too worried."