Olympic 400m freestyle champion Ahmed Hafnaoui said on Wednesday he was unsure he would be fit to defend his title in Paris.
"I'm currently suffering from an injury, and I don't know whether or not I will participate in the Olympics," the 21-year-old Tunisian swimmer told AFP in a phone interview.
He did not give details of the injury.
Mehrez Boussayene, head of the Tunisian Olympic Committee, told AFP "nothing is confirmed", adding the swimmer had a "developing injury".
"More than just medals, we seek above all the well-being of this young man who brought us so much joy," said Boussayene. "He will have other world competitions."
After winning gold in Tokyo as an 18-year-old in 2021, Hafnaoui won the 800m and 1500m freestyle titles at last year's World Championships in Fukuoka, Japan.
If he swims in Paris this summer, he has a chance to match Tunisia's top Olympic swimmer Oussama Mellouli, who won two golds and a bronze over the 2008 and 2012 Games.
The country's top Olympic medallist is long-distance runner Mohammed Gammoudi, winner of four medals, including one gold in the 5 000m in 1968, between 1964 and 1972.