British Tour de France star Mark Cavendish will face sprint rival Tyler Farrar at the London 2012 road race test event in Surrey on 14 August.
Cavendish won the Tour green jersey last month but American Farrar won a stage and was a consistent threat.
The Surrey Cycle Classic covers the 140km Olympic course, with the start and finish on The Mall.
Organisers expect Olympic track champion Ed Clancy to be part of a five-man GB team, including Cavendish.
The event mixes national teams with British trade line-ups but the top athletes will all be competing for their countries.
Cavendish, who learned on Thursday that his HTC-Highroad team will fold at the end of the season, will line up in GB colours alongside several riders from Team Sky, the outfit he is being tipped to join next year.
Great Britain will gain an early chance to scout the route where Cavendish is favourite to win the first gold of the Games on 28 July 2012.
The event will also provide a valuable opportunity for Cavendish to spend time with the GB squad ahead of the Road World Championships in Copenhagen in September, where he is also expected to star.
Although the final 148-man field has not yet been confirmed, Cavendish's HTC team-mate Matt Goss is set to ride for Australia and French champion Sylvain Chavanel will also feature.
The race passes through six London boroughs and four Royal Parks, with a looped route around Box Hill in Surrey.
Spectators can view the action for free along much of the route, although they are being advised to avoid Box Hill, which is a site of special scientific interest and has restricted access.