Vettel admits: I could have been better.

Despite his relative lack of Formula One experience, Sebastian Vettel admitted to being disappointed with seventh on the grid for his Formula One debut at the US Grand Prix.

Although the result mirrored those being achieved by Robert Kubica so far this season, Vettel - who is subbing for the Pole following his Montreal shunt last Sunday - reckoned that he could have been closer to team-mate Nick Heidfeld.

"Qualifying was thrilling as you have three different sessions and three times the opportunity to either do a good lap or a bad lap," he admitted, "Towards the end, I could have been a bit better, but making it into qualifying three was already a big step.

"I shall sleep better tonight because, last night, I had the unknown ahead about what will happen. However, yesterday, I think we had a very good day and today also was not too bad. Here I shall be racing against the best drivers in the world, which is a big challenge, and the race is a bit longer than I am used to. Now I am much more familiar with the car, I am really looking forward to the race"

Team boss Mario Theissen, however, was pleased with the way his prot?g? had handled his first qualifying session.

"Sebastian did a very good job," he insisted, "He did exactly what we asked him to do. He was able to concentrate, stayed calm and focused."