Speaking to Germany's Bild am Sonntag newspaper, Niki Lauda admitted he has been trying to convince Vettel to join Mercedes, whose current drivers are Lewis Hamilton and Nico Rosberg.
"I continued what (former motor sport director Norbert) Haug began," said Lauda, Mercedes' new chairman and shareholder.
Fellow Austrian Marko, who is Red Bull's F1 consultant, insisted he has no hard feelings.
"Niki should absolutely be trying to get Vettel," he said.
The news gives fresh insight into the driver rumblings at Red Bull, amid Mark Webber's possible exit at the end of the year, and rumours Kimi Raikkonen is being courted.
"Red Bull need to ensure that if Sebastian Vettel gets the mega-offer from Ferrari and leaves, they have their tail covered and Raikkonen would be very capable of that," technical expert Gary Anderson told the BBC.
"I believe he (Raikkonen) is a perfect fit for Red Bull. I wouldn't be surprised if negotiations were well down the road for this to happen," he added.
Similarly, David Coulthard thinks Lotus might be hard-pressed to convince Raikkonen to stay, if powerful Red Bull comes knocking.
"They definitely have good people there (at Lotus)," he told Germany's motorsport-magazin.com, "but it looks like not the same financial setup (as Red Bull)."
Coulthard said his former teammate Mark Webber is still doing a good job, "but the link between Kimi and Red Bull goes way back".
"If Mark decides to do something else, in my view Kimi would be the perfect teammate for Sebastian."
For now, Raikkonen's public comments on the matter are guarded.
"I don't have a contract (beyond 2013)," he told Finland's Turun Sanomat newspaper, "but at some point I have to think about it.
"I want to win, and at least for the moment, I want to be here (at Lotus)."
Some have named the 2007 world champion as Vettel's most likely challenger for the 2013 title, but 33-year-old Raikkonen is not so sure.
"It's going to be hard to catch Sebastian if he keeps taking good results so we need to start taking more points from him," the Finn said.