Daniel Ricciardo will drive for Toro Rosso in Friday practice sessions at all grands prix in 2011, the team has announced.
The Australian, a product of Red Bull's driver development system, was already a reserve for both Red Bull Racing and Toro Rosso, and dominated the recent Abu Dhabi rookie test for the former team.
Ricciardo will replace one of Toro Rosso's race drivers, Sebastien Buemi and Jaime Alguersuari, in practice at each event, with the two drivers alternating in stepping aside for the 21-year-old.
Team boss Franz Tost welcomed Ricciardo's promotion and joked that it would keep Buemi and Alguersuari on their toes.
"When our team was created, its stated aim was to bring on young drivers from the Red Bull Junior Programme, so Daniel's appointment as our third driver is an obvious one," he said.
"Although Daniel has done some F1 testing already, running on Fridays at the grands prix will give him a valuable insight into the additional pressures of doing it for real during a race weekend.
"I am also sure that having a hungry youngster on the books will keep our current driver pairing nice and sharp!"
Ricciardo will also contest the Formula Renault 3.5 series again next season. He finished second in the championship at the first attempt this year.
"I am really excited at the prospect of driving for Scuderia Toro Rosso in the free practice one sessions at the grands prix next year, so I have to say thanks to Red Bull for this great opportunity," he said.
"My main priority for 2011 is to win the Formula Renault 3.5 championship, but my ultimate aim is to be a full-time Formula 1 driver and this new role has to be the best step towards achieving that ambition."