The president of 2024 Paris Olympics has said the triathlon competition could be delayed or cancelled amid fears over the water quality of the River Seine.
The Paris organising committee are placing the Seine at the heart of this year's Games, with the opening ceremony set to take place on the water rather than in a stadium for the first time in history.
The river is also due to be the site of the swimming leg of the triathlon, followed by bike and running routes that feature the Champs-Élysées before finishing on the Pont Alexandre III.
Paris officials have been working on cleaning up the Seine so that people can swim in it again, as was the case during the 1900 Paris Olympics. But a sewer problem last summer has already led to the cancellation of a pre-Olympics swimming event.
Paris Mayor Anne Hidalgo has promised the river will be clean enough to host the Olympics, even saying last month she intends to take a dip herself and invited French President Emmanuel Macron to join her.
However, the Paris organising committee president Tony Estanguet told the SportAccord conference that the planned triathlon event could be severely impacted by the water quality.
"We are working hard on it; you know it's one of the bigger challenges," Estanguet said. "When we decided to have this competition in the Seine we knew it will be a big challenge but with the authorities, there is a big programme of investment and, when we talk about legacy, this project is fantastic.
"We are still confident that the triathlon will be based in the Seine because we have contingency plans. We can postpone for rainy conditions. Because it's programmed at the beginning of the Games we can wait for better conditions. So we are confident that it will be possible to use the Seine.
"We change the date and postpone from one day to three days until it's OK. And there is a final decision where we could not swim -- it's part of the rules of the International Federation. It's what we want to avoid, of course.
"But there's a risk. There's always a risk. I was an athlete. I attended World Championships that were postponed because of floods. When you are in a sport where you rely on the natural conditions, you have to adapt. It's part of the flexibility in my sport."