Austria's Christian Klien and Italy's Vitantonio Liuzzi signed contracts for the Formula One season with Red Bull Racing, the team said on Wednesday.
The pair join David Coulthard, who signed a one-year contract with the Austrian team last month, but Red Bull said it had not yet decided which of the two would be its second driver.
"Christian Klien and Vitantonio Liuzzi signed for Red Bull Racing this week," Red Bull said in a statement, adding that the two had signed identical one-year contracts with an option for additional years.
"The team management at Red Bull Racing will decide after tests in January and February who will start alongside David Coulthard in Melbourne," it said.
Coulthard signed a one-year contract last month with Austrian billionaire Dietrich Mateschitz who bought the Jaguar team from Ford and renamed it after his energy drink brand.
Klien has the advantage of a year in Formula One racing with Jaguar. Liuzzi, the Italian Formula 3000 champion, is seen as a dazzling prospect for the future.
Coulthard, 33, lost his drive at McLaren to Colombian Juan Pablo Montoya last year and the Scot's prospects had looked bleak until Red Bull came along.
The Formula One season opens with the Australian Grand Prix in Melbourne on March 6.
