Red Bull's Sebastian Vettel has expressed his excitement at the prospect of winning his third world championship title in a row.

The 25-year-old will head into this weekend's US Grand Prix 10 points clear of Ferrari's Fernando Alonso at the top of the standings.

"It has been a very long year - a tough season up and down, extremely challenging, different to previous years in many ways, we learned a lot and we did less mistakes this year," BBC Sport quotes the German as saying.

"We have a very competitive car - we had one since the beginning of the season, maybe sometimes not good to win, but still good enough to collect a lot of points.

"It put us in a strong position, we are able to fight for championship with two races to go. It would mean a lot [to win the title] but it's difficult now to find the right words."

Vettel won the world championship title in 2010 and 2011.