Austrian Christian Klien will race the next four Grands Prix for Red Bull and probably the two after that as well, team boss Christian Horner said on Thursday.

"Christian will certainly do the next four races, they are both back to back events -- here to Indianapolis and Magny-Cours to Silverstone," he said at the Canadian Formula One Grand Prix.

"We'll just keep evaluating the situation but it's most likely he will do the following sequence of back-to-backs as well from Germany [Images] to Budapest," added Horner.

Klien is returning to the race seat in Montreal after trading places with Italian Vitantonio Liuzzi, who competed in the last four grands prix, as part of a pre-arranged share.

Liuzzi is being rested for Canada [Images] and the following U.S. Grand Prix with American Scott Speed taking on the Friday practice role.

Formula One is in the busiest part of a 19-race season, with eight races in nine weeks.

The French Grand Prix is on July 3 and the British at Silverstone on July 10.

Red Bull, owned by energy drink billionaire Dietrich Mateschitz who bought the Jaguar team last November, are sixth in the championship with 19 points, all but four scored by Briton David Coulthard.

Klien said the team had been surprised by their strong start to the year.

"It will get more difficult during the season because the bigger teams can develop the car more than us," said the Austrian.

"But we saw at the Nuerburgring that we are still competitive and with a bit of luck we can both drive in the points and I hope we can get some points this weekend."

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