The German would form a 'dream team' with Fernando Alonso in the most sensational Formula One transfer for years - the pair are widely considered the two best drivers on the grid.
Felipe Massa is thought to have agreed a deal to stay with Ferrari in 2013 before making way for Vettel.
The BBC reports that Vettel's Ferrari contract is likely to stipulate a minimum performance level in 2013, below which he could pull out of the deal.
The team's current lead driver Alonso is thought to have sanctioned the deal, having previously vetoed a move for Lewis Hamilton - his former team-mate at McLaren where they endured a stormy relationship.
Vettel and Alonso lie first and second in the drivers' title race, separated by six points with four races left.
Asked about the Massa situation at the Korean Grand Prix, Ferrari team boss Stefano Domenicali said: "Very soon you will know what will be our position on that respect.
"I think that for sure he understands now better the car, he understands better the tyres – and also the fact Felipe is a very, very strong driver because otherwise we would have already taken a different decision.
"So I feel that now when Felipe has under his control the understanding of the tyres and car, he performs at the level he should."
Vettel, meanwhile, has been installed as a strong favourite for the title following his win at Yeongnam on Sunday.
He has won three races in a row, outscoring Alonso 75 points to 30 over that time.
Red Bull team principal Christian Horner said: "We've hit a purple patch of form at the right time but it's important we maintain that now. There's still a long way to go,"
Domenicali added: "Clearly at the moment Red Bull might seem unbeatable in everyone's eyes, but I can remember the same thing being said about McLaren on (the) Sunday afternoon in Singapore. The wheel turns quickly this year."
- Fernando Alonso
- Felipe Massa