Sebastian Vettel handed 10-place grid penalty at United States GP

Sebastian Vettel is 66 points behind Lewis Hamilton in the drivers' standings with four races left

Lewis Hamilton's chances of securing the world title at Sunday's US Grand Prix have been boosted by an engine penalty for Ferrari's Sebastian Vettel.

The German, 28, will be demoted 10 places on the grid after using more than the permitted number of engines.

Hamilton, 30, will win the title if he outscores Vettel by nine points and Mercedes team-mate Nico Rosberg by two.

If Hamilton wins in Austin with Vettel below second, the Briton will clinch his third world championship.

However, if Hamilton is beaten by either driver, the title race will remain open until at least the race in Mexico next weekend.

"If you look at this race isolated it is not great news, but it was always the plan to have a fresh engine here," said Vettel.

"The plan was to have maximum power in every race. We take a hit here but you have to see the positive in that we were able to make big steps and not just the penalty."

Vettel will take a 10-place penalty for using a fifth engine - one more than is allowed under Formula 1 rules - while Ferrari team-mate Kimi Raikkonen has been given a similar punishment.

Lewis Hamilton has 302 points, compared to 236 for Sebastian Vettel

Meanwhile, Fernando Alonso said Hamilton had already attained the status of one of the greatest drivers of all time.

"He is one of the best in the sport and I think there are more titles to come," said Alonso, who has also won the world championship twice.

"He had some ups and downs but the good thing about Lewis is that when he didn't have the best car he still won some races, maybe not the championship but still winning some races and fighting for the championship.

"That is something maybe not everyone did."

Alonso and Hamilton have consistently cited each other as their biggest rival, the driver for whom they have the most respect.

Asked whether Hamilton could go on to match or beat the five titles won by Juan Manuel Fangio or even Michael Schumacher's all-time record of seven, Alonso said: "That is difficult to tell. It depends a lot in the car.

"He won in the second year and then until he arrived at Mercedes he could retire maybe with one title.

"Maybe he can win no six if no-one can beat Mercedes in the next years. It is difficult today. But rating a driver takes much more than a title."

In his BBC Sport column, Hamilton said he was not contemplating wrapping up the title this weekend.

Mercedes team-mate Rosberg still has an outside chance of winning the drivers' championship, but is 73 points behind Hamilton.

"I've got nothing to lose - I want to win," said Rosberg. "I have the opportunity to win and it's a great target to have. I'm focused. That's it.

"I'm still aiming for first and that's what I'm thinking about, even if I know it's difficult and I need a lot of luck."