The men's triathlon at the Paris Olympics will not go ahead as planned on Tuesday as pollution levels in the Seine remain too high, World Triathlon said in a statement, dealing a blow to organisers and leaving athletes facing more uncertainty.

The race was postponed to Wednesday at 10:45 a.m. (0845 GMT), immediately after the women's event, which is scheduled for 8 a.m. that day.

Organisers previously said they were confident water quality would improve in time for the race after heavy rains last Friday and Saturday dirtied the river.

"Despite the improvement of water quality levels over the last hours, the readings at some points of the swim course are still above the acceptable limits," they said early on Tuesday.

"Paris 2024 and World Triathlon reiterate that their priority is the health of the athletes."

Should levels of bacteria remain too high by Wednesday morning both the men's and women's races are likely to be postponed to Friday, the contingency day reserved for the events.

If by Friday the water quality is still not good enough the swim leg will be scrapped and athletes will compete in a duathlon instead.

For the mixed triathlon relay event on Aug. 5, the contingency day is Aug. 6.

Paris authorities have promised to make the Seine swimmable as a key legacy of the Games, and spent 1.4 billion euros ($1.51 billion) on wastewater infrastructure to contain sewage and minimise spillage into the waterway.

Paris Mayor Anne Hidalgo took a dip in the river herself earlier this month, in a bid to convince doubters.

The gamble that the river would be clean enough on the day of the triathlon was never guaranteed to pay off, especially as water quality varies widely day-to-day.

Rain significantly increases concentrations of infection-causing bacteria like E. coli and enterococci.

Seth Rider, one of 55 triathletes entered in the men's race, has told reporters he took unconventional measures to prepare for exposure to bacteria.

"We know that there's going to be some E. coli exposure, so I just try to increase my E. coli threshold by exposing myself to a bit of E. coli in your day-to-day life," the U.S. athlete said in a press conference on Saturday.

The Olympic triathlon course was conceived to maximise the wow factor, with the river swim a key element.

After diving into the Seine from a pontoon next to the Alexandre III bridge, athletes are set to race past the Musée d'Orsay and Grand Palais during the bike and run elements before ending back where they started.

Crossing the finish line on the bridge, competitors will be framed by stone columns topped with gilt-bronze statues of Pegasus, with the golden dome of the early 18th century Invalides monument as a backdrop.