Alonso signing up to Mercedes would have meant reuniting with Hamilton, almost a decade on from their fractious year as McLaren team-mates in the Brit’s rookie F1 season.
“I’ve had contact with Mercedes in the past,” Alonso told the Man in Town magazine.
“Back in 2016, when Nico Rosberg decided to retire, I spoke with Toto Wolff, but we never reached a definite agreement.”
The Silver Arrows are seemingly one of few teams that could tempt Alonso back to F1, with the Spaniard only interested in a return if a genuine title bid is on the cards.
“In the future, I’m open to interesting offers,” he said.
“If I decide to return to Formula 1, it’ll only be if there’s a real possibility of winning the world title.
“I’m not interested in projects that are starting from zero. I want a car immediately capable of winning.
“If Formula 1 becomes attractive again, I have no doubt that I would return.”