Asked if the other team was Ferrari, he said: "You can make whatever assumption you want".
Lewis Hamilton will start today's race from down in 14th
"I said from day one 'I am not looking anywhere else?" I think we have done a really good job considering certain things that we've faced and what they have brought to different races.
Mercedes Motorsport boss Toto Wolff was equally confident about the two parties' decision to stick together.
Denmark's Kevin Magnussen made the most of Hamilton's absence from the final phase by putting his Ferrari-powered Haas into fifth place with French team mate Romain Grosjean sixth. I'm not talking to anyone else. I'm not playing you against anybody else.
Now 15th thanks to setting a time good enough to escape Q1 before the problem, he will move up a place thanks to Daniel Ricciardo's penalties - subject to incurring any grid drops himself. "So, we can take our time".
Friday's running, however, suggested that there was little to separate the top three teams as Red Bull were fastest in both sessions - Daniel Ricciardo in the morning and Max Verstappen in the afternoon.
Hamilton explained that he had agreed a basic contract by the time of the Monaco Grand Prix in late May, but subsequent delays were due to his own preoccupation with details.
"I jumped out and wanted to push it back but it was so far to go".
"It just kept getting better and better, and I knew in the last lap I had more in me and I was able to squeeze everything out", Vettel said of his lap.
"I wasn't expecting to feel as excited as I am now in signing this extension". In total, he has 61 Formula One wins over the course of his career, second only to Michael Schumacher.