Audi begins the countdown for a successful defence of its Le Mans 24 Hour motor race title by contesting important warm-up trials in France on Sunday.

The German prestige car manufacturer is bidding to win the annual, classic round-the-clock marathon for a third consecutive year and has recruited ex-Formula One star Johnny Herbert into its factory squad for the race on June 15/16.

Herbert, 37, who retired from Grand Prix racing in 2000, will drive the latest 200 mph Infineon Audi R8 sports racing car.

On Sunday, Johnny and the other members of the Audi Sport squad, will grab their only opportunity of making detail adjustments to the car's suspension and aerodynamics specific to the challenge of the recently-revised 8.62-mile LeMans circuit.

"We'll fine-tune the cars so that when we arrive back at Le Mans in June for the race itself, we have the best possible set-up," said Johnny.

"The Le Mans circuit is made up of public roads and is only closed off on this one occasion before the race so it's vital we get a lot of work done on Sunday.

"Nowadays these machines are basically a Formula One car enveloped in a wide, sportscar body.

"Much of the same technology is present like paddles behind the steering wheel to change up and down the six-speed sequential gearbox for example."

Herbert will partner Rinaldo Capello and fellow Italian Christian Pescatori in their Audi R8.

Powered by a twin-turbocharged 3.6-litre V8 engine featuring the latest FSI (petrol direct injection) technology and producing in excess of 600bhp, they will need to average around 130mph for 24 hours covering over 3,200-miles to be in contention for honours.

"I won Le Mans in 1991 and the Audi R8 gives me a great opportunity of a second career win in what remains one of the world's great motor races," added Johnny.

"I won the Sebring 12 Hour race two months ago which gives us a lot of confidence."

Tipping the scales on the minimum weight limit of 900kgs (17cwt) about the same weight as an Audi A2 the R8 can accelerate from rest to 62mph in 3.2seconds, 124mph in under 7secs and 186mph in 17secs despite the engine being restricted due to regulations.

Importantly, it can come to a halt from 186 mph in 4.0 secs less than 160 yards.

Having dominated world rallying and touring car racing in the eighties and nineties respectively with cars featuring its unique quattro four-wheel-drive system, Audi switched to endurance sportscar racing in 1999.

In 2000, Audi finished 1-2-3 at Le Mans and claimed a 1-2 result with its two-car "factory" entry last year.

Audi's 1996 British Touring Car Champion Frank Biela, Emanuele Pirro and Tom Kristensen have been victorious at Le Mans for the past two years and will make history should they sweep their R8 to victory this year as the same three driver crew has never had three successive wins.