SPA-FRANCORCHAMPS, Belgium (AP) — Four-time Formula One champion Sebastian Vettel says it was a "no-brainer" to extend his contract with Ferrari for three more years but it still took him until late August to do so.

The German driver, who was out of contract at the end of this season after joining from Red Bull in 2015, penned a new deal until the end of 2020 this weekend. Ferrari made the announcement in a statement Saturday at the Belgian Grand Prix, without giving further details.

"I decided to go for it and make the call," Vettel said after qualifying in second place for Sunday's race. "I love this team and I love the people I work with. I believe that Ferrari has something unique, something the other teams don't have."

Earlier this week, Ferrari also extended Kimi Raikkonen's contract, although only for one year.

Since joining Ferrari, Vettel has won seven races — three in 2015 and four this year — and secured 28 podium finishes. His win at the Hungarian GP before the summer break was the 46th of his career.

"The presence of Ferrari is huge. But if you see the people working at Ferrari and meet them, it's even bigger, the passion they carry inside them," Vettel said. "That's my conviction. It was a no-brainer to continue. We haven't yet achieved what we want to, but things are looking pretty good."

Ferrari clinched its last drivers' title in 2007 — when Raikkonen won in his first stint there — and its last constructors' title the year after.

This announcement ended speculation as to whether the 30-year-old Vettel was going to stay with the Italian team, or potentially make a move to rival Mercedes next year. Mercedes driver Lewis Hamilton, who trails Vettel by 14 points in this year's title race, scoffed at that prospect on Thursday, saying Vettel would not want to be his teammate.

But asked if he had considered a move to Mercedes — having reportedly discussed it with Mercedes' management — Vettel was ambiguous.

"I've been around in the paddock for a while so I know people; it's natural that you talk. But nothing more than chatting, mostly about other stuff to be honest," he said. "I've been talking for a while with Ferrari, my intention was to stay. I want to win in red. Michael (Schumacher) won most of his championships in red."

The next three years are locked down for Vettel, but he sounded cautious about whether he wants to end his career with Ferrari.

"We'll cross that bridge when we come to it," he said. "It's a long time; a lot of things can happen ... That's far, far away, so not really a topic."

The news of Vettel's signature could also have a knock-on effect on Mercedes. With Vettel unavailable, and Red Bull duo Max Verstappen and Daniel Ricciardo tied to contracts next year, this increases the chances of Valtteri Bottas staying with Mercedes next year.

Bottas joined late last year as an emergency replacement for Nico Rosberg, after the German driver stunned F1 by retiring days after beating Hamilton to the title.

The 32-year-old Hamilton has another year left to run on his Mercedes contract.