Red Bull Racing endured a modest afternoon of testing in practice for the United States Grand Prix at Indianapolis, both David Coulthard and Mark Webber bothering the top ten positions in both sessions.

Spending the day chasing a good set-up for the weekend, the high temperatures made matters tricky for most of the teams, with Coulthard himself admitting to almost suffering some off-track moments.

Even so, eighth and sixth fastest in the morning and afternoon sessions respectively gave the Scot an encouraging start to the weekend to build upon.

"They were pretty hectic sessions today. We have very high track temperatures and with the low downforce that we run here, the car's quite tricky to drive. I didn't actually go off the circuit, but there were a lot of moments. The times are encouraging."

Webber meanwhile emerged tenth and 12th best following the two sessions, but after suffering a transmission failure, he added he needed additional track time to fettle his car ahead of what promises to be a very tight qualification session.

"Today didn't quite go to plan, especially in terms of completing our programme. We were working quite hard on the balance, trying to adjust it and get it to a place where I was happy with it. We needed a bit more track time, but then we had a transmission failure, which cut short the day. It's pretty tight between all the cars, it always is round here, so now we'll just look to tomorrow."