Klien Safe for Next Four Races

But team owner Dietrich Mateschitz suggested Klien could continue to drive after those four events.

"I would say, Christian drives until further notice. For sure the next four events," Mateschitz told Motorsport Aktuell. "After that we have to see if there are new possibilities. We will do our level best to meet the expectations of both drivers.

"If there is no other way, Liuzzi might come back for one or two races. We had thought that Tonio deserves another chance after Monaco. It would not have been good for him to take him out of the car at that point in time. He drove a incredibly strong qualifying lap at the Nurburgring.

"There is no doubt about his potential. But at the same time we believe that it is right to allow Klien now a certain amount of races and a certain continuity."

Red Bull's race drivers in Canada will be Briton David Coulthard and Klien, who replaces Italian Vitantonio Liuzzi after filling the third driver slot for the last four races.

Liuzzi, the last F3000 champion, scored a point at the San Marino Grand Prix while Klien scored twice during his three outings.

The Italian will be sidelined for the Canadian and US Grands Prix, with American Scott Speed driving the third Red Bull on Fridays.

The young Californian impressed the team in testing at Barcelona and Silverstone, and Mateschitz believes he could land Red Bull's third seat next season.

"I could well see him as test driver for us in 2006," he added.