Time is running out for Lewis Hamilton in his bid to catch Nico Rosberg in the Formula One title race ahead of the United States Grand Prix.

Rosberg holds a 33-point lead over his Mercedes team-mate with four races left this season.

Hamilton has won the past two, and three of four, races in Austin and another victory would put the pressure on Rosberg.

However, the Brit is winless since Germany, a run of five races – four of which Rosberg has won to pull clear atop the drivers' championship.

HAMILTON LOOKS TO CORRECT STARTS

A bad start proved particularly costly for Hamilton in Japan before he recovered to finish third in a race easily won by Rosberg.

The three-time world champion knows change is needed, and it is an area he has worked on.

"It has been an ongoing thing all year long - perhaps more work than in other areas," Hamilton said.

"I was working on it at the factory last week and we hope we have a better formula this weekend."

VETTEL BACKS HAMILTON

Sebastian Vettel, winner in the United States in 2013 to break Hamilton's run in Austin, believes the Brit can catch Rosberg.

The Ferrari driver, sixth in the standings, said he would love to be in Hamilton's position.

"It's realistic because I think he's quick enough," Vettel said.

"It's realistic because there's a lot of points to get and I think it would be quite bad if you quit now.

"If I could swap, I would immediately and go for it, so I'm sure that he goes for it and four races is a lot of laps to do, a lot of things that can happen so it's only over when it's over."

HAAS AT HOME

For the first time since 1986, an American team is in F1, a huge boost heading to the Circuit of the Americas.

Haas' debut campaign has been a good one with Romain Grosjean and Esteban Gutierrez.

Grosjean started the season well and has all of the team's 28 points, although recent races have been a struggle.

THE CIRCUIT

The anti-clockwise track has two notable and crucial hairpins.

Turn one is a left-hander approached uphill, while turn 11 is tricky with drivers needing to turn and brake at the same time.

WEATHER FORECAST

Drivers will enjoy sunshine.

Austin is expected to turn on sunny weather from Friday through to Sunday, in contrast to last year's rain.

TYRES

It is softer tyres for teams in USA, with the white medium, yellow soft and red supersoft nominated.

"We're also bringing the supersoft to the track for the very first time," Pirelli motorsport director Paul Hembery said.

"As a result, the free practice sessions in particular will be extremely important this year, with the optimal strategy yet to be defined."