MEXICO CITY -- Lewis Hamilton is riding a "positive wave" as he inches toward his fifth world championship, but has warned his rivals he will not be resting on his laurels once he has secured it.

Hamilton only needs to finish seventh at one of the remaining three races of the season to clinch his year's crown, while Sebastian Vettel has to win at the Mexican Grand Prix to have a chance of taking the fight to Brazil. The Mercedes driver has wrestled the initiative away from Vettel in recent months with a stunning run of six wins in eight races.

Before joining Mercedes as a one-time world champion, Hamilton said he would not have been happy leaving F1 without winning another.

When asked on Thursday how he felt as he now stood on the verge of a fifth, he said: "I've still got more to do. There are so many different things that happened in that time and I waited a long time to get the second.

"I could easily have stayed where I was and I wouldn't be sitting here with the ones I have now. It's been interesting, the journey and the different decisions I have taken, but I am very grateful for the route that I have been on. I feel incredibly fortunate to be in the position I am in, but I feel like I have quite a lot left to do."

Hamilton has won the Mexican Grand Prix on one previous occasion, in 2016. Charles Coates/Getty Images

Hamilton came to last weekend's U.S. Grand Prix with a shot at wrapping up the championship but was in a relaxed frame of mind, which appeared to be the case again during the media day for the race at Mexico City's Autodromo Hermanos Rodriguez.

Explaining his outlook, he said: "It's not my first rodeo. I'm guessing that's just the place that I am at in my life, being that I am a bit older, and I have the experience to know what I need to do to get myself into shape, and I'm just really enjoying racing. I'm here to win, I'm here to win, and I'm here to win this championship with the team, so I choose what I want to put my focus towards and I don't allow any negativity in.

"So I'm just on a positive wave. I'm sure if I was here and there was one point between us it would be different and more intense, but I'm a decent amount of points ahead, so I guess that does naturally help a little bit, but I think it's just the experience."