Lewis Hamilton won't take risks in US GP to seal 2015 F1 title

Hamilton will line up second on the grid at Austin behind Mercedes team-mate Nico Rosberg following a curtailed qualifying session in which heavy rain prevented any running in Q3, resulting in the times from Q2 determining the grid.

To become a three-time world champion Hamilton has to finish two points better off than Rosberg and nine ahead of Sebastian Vettel, who starts 15th in his Ferrari as he serves a 10-place grid penalty for an engine change.

"With qualifying cut short I was unable to battle it out in last few laps [with Rosberg]," said Hamilton.

"But qualifying is just the beginning. The race is a long battle, and it's going to be hard out there in those conditions, and throughout the race.

"So today it's about being sensible out there, there is no need to take any particular risks.

"There are four races [available to take the title] so it's not do or die this weekend.

"You have to appreciate it's incredibly tricky. The conditions are varying from corner to corner throughout the lap, so you are basically on your tiptoes the whole time.

"You have to apply these techniques you learned in the early days of driving, in terms of finding the grip, in terms of being sharp and reacting to aquaplaning moments which you never expect.

"It's to the point where you are throwing the car into the corners, attaching the grip and keeping going without lifting.

"It is about being very sensitive, but as smooth as you can be, and as cautious."

In contrast, Red Bull's Daniel Ricciardo, who lines up third, has nothing to lose and is ready to attack the all-Mercedes front row.

"In these conditions there is always a fine line, but you're better off being more on the side of risk, because if you don't drive in these conditions with confidence then you don't get far," said Ricciardo.

"If there is a bit of aquaplaning or a bit more rain starts, and it scares you or makes you a bit more cautious, then everyone is going to jump in front.

"So you definitely need to drive in these conditions with confidence, and I'd say a little bit of aggression.

"It can bite you, but risks need to be taken because it can make or break you in these conditions.

"For us as a team and me as a driver, I'm not fighting for a championship, and these conditions are good for us.

"It's an opportunity in the rain, so to put it all on the line makes sense."