Sebastian Vettel has conceded that it would be special to clinch his third F1 drivers' world championship title this weekend, with the inaugural USGP at the new Circuit of the Americas coinciding with his 100th start.

The Red Bull driver has overcome a 44-point deficit to sole remaining rival Fernando Alonso since the German Grand Prix, finally passing the Spaniard when he won the Japanese round and the Ferrari spun out at turn one. Since then, Vettel has ensured that the RB8 has been the car to beat, only faltering in Abu Dhabi when forced to start at the back of the grid following four straight victories to start the end-of-season 'flyaways'.

The German needs to finish 15 points ahead of Alonso if he is to win the title in America - the equivalent of winning with the Spaniard outside the top four or making the podium with Alonso failing to break the top ten - and Vettel admits that it would be an incredible feat to achieve.

"It has been a very tough season - up and down, I think, for everyone," he reflected, "[It has been] extremely challenging, different to previous years in many ways. I think we learned a lot and did way less mistakes this year. We have a very competitive car, we've had one since the start of the season, [although] maybe sometimes not good enough to win, but still good enough to collect a lot of points. I think that put us in a very strong position.

"There are only two races to go, so whatever happens this weekend, we have to make sure we get the maximum on Friday [and] Saturday, because the points are there to grab on Sunday and not before. But, for sure, it would mean a lot, and it's probably difficult now to find the right words."

Completing the symmetry, Vettel's F1 race debut also came on American soil, in the 2007 race at Indianapolis - the last USGP prior to this year - and he recalls that day with clarity.

"[It's something] I think you can't forget," he admitted, "There are some positives, some negatives. I didn't have the best start, and not the best first corner, but then it was quite an interesting race. And obviously a big challenge at the end of the race. I was physically destroyed - I remember that as well.

"I knew that I had a lot to do, but I knew as well that's what I wanted to do in the future. Sitting here, 100 races later, is quite crazy in a way. I think, if the number gives you anything, it's just that you don't realise how quickly time goes by. I think it's always like that when you do something you enjoy a lot. You don't count the days and the months and the years going by. Looking back now, it doesn't seem a long time ago but, looking on the calendar, it's five years ago...."