Rohan Dennis says he made the "right decision" to withdraw from the Tour de France but offered no explanation for mysteriously pulling out on Thursday.

The Bahrain-Merida rider stepped off his bike during the 209.5-kilometre 12th stage from Toulouse to Bagneres-de-Bigorre.

Dennis was well fancied to win the time trial in Pau on Friday, so there was confusion when no reason was given for the Australian ending his participation in the most prestigious Grand Tour race.

The reigning TT world champion broke his silence in a press release issued by his team.

"I am very disappointed to leave the race at this point. Obviously the individual time trial had been a big goal for me and the team, but given my current feeling it was the right decision to withdraw," said Dennis.

"I wish my team-mates the very best for the remainder of the race and would like to thank all the Tour de France fans who cheered for me, at home and on the roadside, since Brussels.

"I will hopefully be back competing in this great race again over the coming seasons."