Scott Sharp will not defend his American Le Mans Series LMP1 title next year after deciding to leave Highcroft Racing.
The 41-year-old American had been expected to continue with Duncan Dayton's Acura squad, despite announcing earlier this month that he had set up his own team, Extreme Speed Motorsports, to run in the GT2 class next year.
But he has now decided instead to step down to GT2 to share one of his Ferrari 430s with Ed Brown, who raced in the Challenge class this year. Extreme Speed will be backed by Patron, which will also retain its sponsorship of Highcroft.
"It was always my intention to come back and defend my championship win with the Highcroft boys in 2010, but after I started the process of getting everything established for Extreme Speed Motorsports, I quickly realised the amount of work we have ahead of us," said Sharp.
"I don't want to do anything at less than 100 per cent. It wouldn't have been fair to them if I wasn't able to be absolutely committed to defending the championship. Also in establishing the new Ferrari team, it also wouldn't be fair if I wasn't able to devote the amount of time required to kick-start the new program.
"I'll really miss working with the guys and driving the prototype cars but the opportunity to establish my own team and really prolong my career way beyond when I eventually hang up my helmet is too good an opportunity to pass up."
David Brabham, who shared this year's title with Sharp, and who will continue as Highcroft's lead driver in 2010, paid tribute to his friend's efforts for Highcroft.
"It has been great to drive with Scott over the past two years," said the Le Mans 24 Hours winner. "We've had some great times both on and off the track and it was a pleasure to share the championship with him.
"He now has a great opportunity ahead of him and while I am sure he may miss driving the prototype, I certainly understand his decision because the opportunity to establish your own team is just fantastic and I know he wants to make sure he gives his new team all the attention it requires."
The team said that it was evaluating potential replacements for Sharp next year.