Hamitlon says his form has been 'shocking'

The Briton has grown increasingly frustrated in recent races as he struggled to match Mercedes team-mate Nico Rosberg, who took podium finishes in the last two grands prix while Hamilton could only manage sixth and seventh places.

"I would say it is since the [summer] break that it has been shocking," said Hamilton in the Austin paddock on Thursday.

"Maybe the direction the car went, I don't really know. I am just as focused, maybe the set-up direction we have been going hasn't been right, but sometimes you feel you have not been in the right place at the right time.

"In Suzuka we should have had a good race, I was really quick, and the wing level I had there was really different to Nico so we should have been really good that weekend, and I was unlucky to get a puncture.

"In the last race the qualifying didn't help and it spiralled down from then on.

"I am hoping this weekend to put myself in a better position. I feel positive for this weekend." Mercedes has hinted at a more 'raceable' set-up for this weekend's United States Grand Prix, and Hamilton said he is open-minded about changes.

"There are pros and cons of having less downforce and having high downforce, in terms of overtaking and being overtaken, so they are looking into that, but it is not decided on yet," he said.

"I have been stuck in a lot of traffic and we just can't go past people so it definitely doesn't make the performance seem so good.

"Generally the car is good over one lap, so the car is quick enough, quicker than a lot of cars, but sometimes in the race we are not able to show that."