SILVERSTONE, England, July 6 (Reuters) - Briton David Coulthard, the oldest driver on the Formula One starting grid, has extended his contract with Red Bull for another year and will again partner Australian Mark Webber in 2008.

Coulthard, 36, has won 13 grands prix from 219 starts and joined Red Bull in 2005 from former champions McLaren after making his debut with Williams in 1994.

"Obviously I'm happy to continue the work with Red Bull," the Scot told a news conference at the British Grand Prix on Friday.

"It was a new challenge when I started there to try and see if I could play my part and help guide the team from the driving seat ... the journey continues.

"We've had a bit of a troubled year this year but the pace has certainly improved and logically we would expect to be able to build on that through the course of this year and into next season," he added.

"My enjoyment of racing remains absolute and my commitment to the team is 100 percent as well."

Coulthard, although outqualified by Webber 7-1 so far this year, scored Renault-powered Red Bull's first points of the season with fifth place in Spain in May.

Webber, who moved from Williams at the end of last season, still has a year to run on his contract. Together, they make up the sport's oldest line-up.

Team boss Christian Horner said he was happy with the performances of both drivers.

"We are in an evolution phase of Red Bull Racing and David's done a very good job for us in the three years that he's been with us," he said.

"It was therefore entirely logical to extend that relationship for a further year."