The Spaniard appeared set to re-sign with Ferrari, but management then became aware that Lewis Hamilton was potentially available - the Briton's latest two-year Mercedes contract actually only containing a fixed one-year term with an option for another season.
With Ferrari president John Elkann and team principal Fred Vasseur able to convince Hamilton to join as team-mate to Charles Leclerc, Sainz has been left without a drive.
While the three-time grand prix winner is highly rated, Mercedes has placed Max Verstappen and junior single-seater star Andrea Kimi Antonelli as its top two targets.
Alternatively, moves to Aston Martin and Red Bull are plausible.
"[I'm] talking obviously to a few because that's what my management team and myself should do when I don't have a job for next year yet," said Sainz, who won the Australian Grand Prix last month.
"So, we're talking to pretty much all of them.
"It's just a matter of going more into detail and seeing the more realistic options and what are the best options for me and for my future, which I don't have any news for you, nothing to say.
"The only thing I would say is that obviously, it's time now to speed everything up a bit and hopefully we can get it sorted sooner rather than later."
Source: Autosport