LAS VEGAS, Nov 20 (Reuters) - Seven times Formula One world champion Lewis Hamilton said on Wednesday he had felt like walking away from Mercedes after a tough race in Brazil this month.

The 39-year-old Briton, the sport's most successful driver, is joining Ferrari at the end of the year and hinted over team radio in Sao Paulo that he might be leaving the team ahead of time.

The comments were played down by Mercedes as aimed at team members who would not be at the last three rounds, but Hamilton told reporters at the Las Vegas Grand Prix he had meant something else.

"In the moment that's how I felt, like I didn't really want to come back after that weekend," he said.

"But I think that's only natural. It's frustrating when you have a season like this, which I'm pretty sure I won't have again, or at least I'll work towards not having again.

"It wasn't a great feeling in that moment, but I'm here, I'm standing strong and I'm going to give it absolutely everything for these last few races."

Hamilton finished 10th in Brazil, with team mate George Russell fourth, and said at the time that it had been "a disaster of a weekend" and the worst the car had ever been.

He had finished 11th in the Saturday sprint.

"If this is the last time I get to perform it was a shame it wasn’t great but (I am) grateful for you," Hamilton had said over the radio.

Hamilton was also asked on Wednesday about comments by Mercedes boss Toto Wolff in a recently published book referring to his driver's "shelf life" and saying the Ferrari move meant he would not have to make the decision to get rid of him.

Wolff subsequently said the comments were taken out of context.

"Honestly, I feel in the best place I've been all year mentally, and considering how bad the last race was, I think that says enough," Hamilton said.

"I'm still here, still fighting and I'm going to continue to push. I've got a team that I genuinely still love, and even though I am leaving, I want to make sure I give them the best I can in these next races.

"If they provide a car that wants to stay on track then hopefully we'll have a better result."

(Writing by Alan Baldwin in London; Editing by Alison Williams)

((alan.baldwin@thomsonreuters.com; +442075427933;))