The Spaniard, 11 points clear of Webber and 21 ahead of McLaren''s Lewis Hamilton with 50 still to be won, is the only man in a position to take the title this weekend.
Fernando Alonso can clinch his third Formula One title in Brazil on Sunday but that is about all that can be said with any certainty as one of the most unpredictable of seasons draws to a close.
If the Ferrari driver wins the year's penultimate race, and Red Bull's Australian Mark Webber finishes no higher than fifth, then he will be celebrating at Interlagos just as in 2005 and 2006 when he won his other championships with Renault.
The Spaniard, 11 points clear of Webber and 21 ahead of McLaren''s Lewis Hamilton with 50 still to be won, is the only man in a position to take the title this weekend.
But, with four rivals still mathematically in the running, nothing can be taken for granted.
"Red Bull are still favourite... maybe we have come away with more than we expected but we know the situation can change from one weekend to the next," he said after winning in South Korea 10 days ago.
Alonso knows that one error or engine failure -- a particular concern for Ferrari given problems earlier in the season -- could vaporise his advantage.
It is entirely possible that the top four in the championship could yet head for the final showdown in Abu Dhabi on Nov. 14 separated by a mere three points.
For that to happen, it would need Alonso to retire in Brazil with Red Bull's Sebastian Vettel winning, McLaren''s Lewis Hamilton following home in second place and Webber fifth.
Changeable conditions
Webber, who flew into Brazil from London on Wednesday morning, won at Interlagos last year after failing to score a point on his previous seven visits to a circuit known for changeable conditions and the odd torrential downpour.
In a season where the overall lead has changed hands eight times already, he could easily repeat his 2009 victory.
Despite that, and Vettel being 25 points behind Alonso, Red Bull are wary of putting all their eggs in one basket as Ferrari have done since Alonso''s controversial ''team orders'' win at the German Grand Prix in July.
"It's impossible to predict what will be the outcome," said Red Bull principal Christian Horner.
"That's why I think the best thing for us to do is to really focus on getting the best out of them, to get our drivers up the front and then see what the mathematics look like."
McLaren, with world champion Jenson Button still mathematically in the hunt but 42 points behind Alonso, are also playing a waiting game with Red Bull just 27 points ahead in the constructors' standings.
"I think we all know there are no team orders, so I think the right thing for a racing driver is to go there and try to win," McLaren team boss Martin Whitmarsh told reporters on Wednesday.
"I'd be disappointed if Jenson wasn''t going there trying to win," he added of the Briton who won his title in Brazil with Brawn a year ago.
Alonso could find team mate Felipe Massa is again a kingmaker, just as he was in 2007 when he gifted former team mate Kimi Raikkonen the win in Brazil so that the Finn could take the title by a single point from Hamilton and the Spaniard.
The Brazilian has won twice before at his home circuit and qualified on pole on his last three appearances.
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