By Alan Baldwin

SAO PAULO - Lewis Hamilton went from despair to exhilaration on Sunday in a Brazilian Grand Prix that left his Formula One title hanging in the balance until the final seconds.

"Amazing, I can't even get my breath back," gasped the Briton, the sport's youngest champion at the age of 23, after a race that had his team chewing their fingernails right to the finish.

When he crossed the finish line, the McLaren driver had no idea whether he was champion or runner-up for the second year in a row.

"I was shouting: 'Do I have it, do I have it?' and then they came on when I was at Turn One and they told me and I was ecstatic. It's been a dream.

"It was one of the toughest races of my life, if not the toughest."

Hamilton had needed only a fifth place for the title and was safely fourth until a sudden downpour six laps from the finish threw the strategy upside down.

He pitted for wet weather tyres and returned in fifth, still safe enough. But three laps from the finish, the Ferrari-powered Toro Rosso of Germany's Sebastian Vettel scythed past and changed all the calculations.

Hamilton began the final lap in sixth place, his family looking on aghast.

Ferrari's Felipe Massa, Hamilton's only rival, took the chequered flag with the home crowd rising to acclaim what looked like Brazil's first champion since the late Ayrton Senna in 1991.

AMAZING ACHIEVEMENT

Salvation came in the form of Toyota's Timo Glock, in fourth place but losing time on dry tyres. Vettel sliced past and then, with the final corner looming, Hamilton was through.

Eighteen seconds later, and one of the most thrilling finales ever witnessed was over.

"I didn't know where Glock was and Vettel was the guy to beat and I couldn't catch him, so at that point I was going to finish sixth. My heart was in my mouth," said Hamilton. "It was absolutely fantastic, an amazing achievement on one of the most troubled days.

"It was such a hard race and I'm ecstatic, very emotional, very thankful for my team and my family and everyone who has supported me."

Hamilton's title was McLaren's first since Mika Hakkinen in 1999 while he was Britain's first world champion since Damon Hill in 1996.

"It's such an amazing achievement for myself, my family and my team who have worked so hard for so many years and they haven't had a championship for so long," said the Briton, the sport's first black driver.

"To be the one that gives them that championship is a real honour."

Hamilton hailed team boss Ron Dennis, who saw the potential in the schoolboy karter who first stood before him at a gala awards ceremony and told him that he wanted to drive for his team one day.

"It's a fairytale story that he gave me that opportunity years ago and he had the foresight to bring me in and groom me to get to this position," he said.

"I've grabbed it with both hands and I've paid him back. I've paid him back in full so I'm happy with that."

(Editing by Pritha Sarkar)