Germany's Sebastian Vettel will replace American Scott Speed at Toro Rosso for this weekend's Hungarian Grand Prix and for the rest of the season, the Italy-based Formula One team said on Tuesday.

Californian Speed, who fell out with team bosses after the last European Grand Prix at the Nuerburgring, was the only American driver on the starting grid and leaves without scoring a point.

Vettel became the youngest driver in Formula One history to score when, aged 19, he finished eighth on his race debut with BMW Sauber in June at the U.S. Grand Prix as a stand-in for Poland's Robert Kubica.

The highly-rated German, also the youngest driver to participate in a grand prix weekend, turned 20 on July 3 and has been the BMW Sauber reserve since last year.

"As our test and reserve driver Sebastian has carried out sterling work for us," said BMW team boss Mario Theissen in a statement.

"However the current testing rules mean that he barely gets a chance to drive for us. Now he has been offered the opportunity to get inside a Toro Rosso cockpit."

Vettel started out with the Red Bull Junior Team at the age of 12 and has been backed by both them and BMW since then, with both teams eyeing him for the future.

"We have sponsored and coached Sebastian over a number of years. To place obstacles in his career path now would go against our concept of talent promotion," said Theissen.

"BMW and Red Bull have a longstanding partnership in supporting Sebastian. Toro Rosso is the sister team of Red Bull Racing and in that context it makes sense for us to release him."

The team said Germany's Timo Glock, who raced for Jordan in 2004 and is now competing in the GP2 support series, would replace Vettel as their reserve.

Toro Rosso did not give a reason for Speed's exit.

However the 24-year-old American made clear after the chaotic Nuerburgring race, where he skidded out early on, that his relationship with team principal Franz Tost and co-owner Gerhard Berger had broken down.

"As far as my future in F1 is concerned, you couldn't pay me enough money to race for those two people again," he said of Tost and Berger in an interview carried on his Web site (www.scottspeed.com).

Speed had also accused the team of wanting to get rid of him and Italian team mate Vitantonio Liuzzi.