The men’s triathlon at the Paris Olympics has been postponed because of concerns over water quality in the River Seine.

Swimming training for the triathletes was cancelled on Sunday and Monday and the decision has been taken to move the men’s race, which had been due to start at 8am local time (4pm AEST) on Tuesday.

It has been rescheduled to take place at 10.45am local time on Wednesday, after the women’s race which is scheduled to take place at 8am.

A statement from World Triathlon said Friday remains a contingency day if one or both of the races are unable to go ahead.

“Tests carried out in the Seine today revealed water quality did not provide sufficient guarantees to allow the event to be held,” read the statement.

“Despite the improvement in the water quality levels, the readings at some points of the swim course are still above the acceptable limits.”

More than one billion euros ($A1.7 billion) was spent on cleaning up the river in preparation for the Games, but organisers knew heavy rain in the days before a competition could cause the levels of the harmful bacteria E. Coli to rise.

There was hope the effects of the deluge that marred Friday’s opening ceremony would have passed in time but that has not been the case.

Britain’s Alex Yee is one of the favourites for gold in the men’s race but he must wait for his moment, while attention now switches to whether the water will be safe for the women’s race.