Toro Rosso expect to retain drivers

"I think we are going to stay with the drivers as we are," the Austrian told a Turkish Grand Prix news conference.

"It's not finally decided but we are quite happy with both of them.

"They are both young, both inexperienced - Tonio a little bit further than Scott but still both very green - and I think under these circumstances they are doing quite a good job," added the former racer.

"We think next year they are going to be more stable and give us back some of what they learned this year."

Speed, 23, is the only U.S. driver in Formula One and his country's first since Michael Andretti left McLaren in 1993.

The Californian's best result so far was ninth in Australia.

Liuzzi, 25, drove four races for sister team Red Bull last year and scored a point on his debut at Imola.

He also finished eighth at Indianapolis this year, taking Toro Rosso's first point since Red Bull bought Minardi and changed the name at the end of 2005.

Red Bull have already confirmed Briton David Coulthard and Australian Mark Webber as their 2007 drivers.