Lewis Hamilton claims he was surprised by his speed advantage over Sebastian Vettel after holding off the Ferrari man to win the United States Grand Prix and close in on the Formula One world title.

Hamilton began the race on pole but found himself behind Vettel following turn one as the German made a flying start at the Circuit of the Americas.

The Mercedes of Hamilton proved too powerful for Vettel, though, who was soon passed by the Briton and he now appears highly unlikely to prevent Hamilton from securing a fourth drivers' championship at next weekend's Mexican Grand Prix. 

"It's been an incredible year so far," Hamilton was quoted as saying by Sky Sports .

"I was not expecting to have the pace on Sebastian we had today but the car felt fantastic.

"I feel amazing. I love this track, I think it's now my favourite track," he said of the purpose-built circuit in Austin, Texas. 

Sunday's results saw Mercedes confirmed as constructors' champion for the fourth year in succession, Hamilton adding: "A big congratulations to the team, they've worked so hard, the guys back in the factory. They've been the best team this year.

"I love my job. It's the greatest feeling in the world. It's a really humbling experience.

"Still three [races] to go and three more to win. Let's go guys."

After watching his early gains swiftly eroded, Vettel acknowledged he was unable to cope with Hamilton's mechanical superiority. 

"At the start it was looking good, we got past Lewis but then fairly quickly we had to realise we couldn't go his pace so congratulations to him," he said.

"Towards the end we decided to pit again for a fresh set of tyres which made the last few laps a bit more exciting. There was no real secret other than they were quicker than us. Whoever is fastest normally has a good chance of winning.

"Then we were in a bit of no man's land. Overall, not the result that we wanted."