Daniel Ricciardo says he is quietly confident Red Bull can maintain their competitive start to the Mexican Grand Prix weekend, suggesting the altitude is helping negate its power disadvantage.

The Australian had predicted the RB11 would struggle down the Autodromo Hermanos Rodriguez's 1.2km straight given the Renault-powered machine's top speed disadvantage, even if he was more confident the car would prove competitive over the remainder of the track.

However, though the Red Bull remains unable to match the Mercedes and Ferrari-powered cars in terms of speed traps, Ricciardo - who ended the day third fastest - says the car nonetheless feels notably quicker and strong in the corners, despite the tricky conditions.

"What you lose from the engines and everything you gain from the corners. The air is so thin, the car is a lot more slippery from what I understand down the straight. It still feels pretty quick and we seem competitive.

Indeed, though Ricciardo is wary of Mercedes, Ferrari and Williams coming on stronger when it matters, he is impressed to be up front out of the box.

"I don't know what Mercedes, Ferrari and Williams have for tomorrow, but seeing as the straight is so long we are doing alright for today."