The time trial specialist, a two-time world champion in the discipline, is among the favourites for the July 28 event and one of Australian cycling's top medal prospects at the Tokyo Games.

The Australian Olympic Committee confirmed on Friday that Dennis would not start in the road race.

It leaves team leader Richie Porte and Olympic debutants Lucas Hamilton and Luke Durbridge as the Australian entries in Saturday's tough 234km road race on day one of the Games.

But most teams are much smaller than usual in professional road cycling, with only Belgium, France, Italy and Spain having the maximum five starters in the field of about 130.

Italy's reigning world champion Filippo Ganna was already confirmed as only racing the time trial at the Games.

While Dennis' absence leaves Australia with one less domestique for the road race, he is a much better medal prospect in the time trial.

Dennis and newly-crowned world BMX freestyle champion Logan Martin shape as Australian cycling's best medal chances in Tokyo.

Dennis won the 2018 and 2019 time trial world titles and was fifth last year behind Ganna.

He was on his way to a likely silver medal in the time trial at the Rio Olympics when a handlebar extension snapped, forcing a bike change that relegated him to fifth place.

His long-time coach Neal Henderson said last week that Dennis has nailed some important test sessions in training and will bring strong form to the time trial.

Australian Associated Press