Vettel secured a second successive drivers' title last season as he dominated the field, finishing over 100 points clear of nearest rival Jenson Button, of McLaren, in the standings.
However, the likes of McLaren, Mercedes and Ferrari have all set their sights on the titles this season, with Red Bull picking up both constructors' and drivers' honours in 2010 and 2011.
Vettel admits that the McLaren's Lewis Hamilton has looked impressive during pre-season testing, although the reigning champion believes it is too soon to know whether McLaren will be able to compete for the top prizes in 2012.
He told Autosport: "I think McLaren looked very strong today. I haven't seen all the lap times yet, I have only had a couple of looks on the long runs that Lewis did today - they seemed to be quite interesting.
"At this stage we are not really talking about the championship for sure. I don't think there is anybody here trying to do worse than last year, so we are trying to do what we did last year, but it's a long way from now."
The first race is set to take place in Australia on March 18 and Vettel admits he doesn't know what to make of Ferrari ahead of the first GP of the season.
He added: "Ferrari is a bit of a secret at this stage and nobody knows whether they are really good or really bad."