The Spaniard told reporters ahead of his home grand prix at Barcelona's Circuit de Catalunya that he did not want to wait any longer.
"I think it's getting to a point where it's obviously taking space out of my head for some weeks and months now," said the 29-year-old.
"I think it's obviously time to make a decision, and the decision will be taken soon. Hopefully, soon we will have things to talk about."
Sainz has been linked most strongly to Swiss-based Sauber, who will become the factory Audi team in 2026, and former champions Williams. Red Bull and Mercedes have closed the door while his previous team McLaren have no vacancy.
Sauber and Williams have made overtures to the Spaniard but assessing how competitive they might be next year, and in 2026 when the engine and chassis rules are changing in a major shake-up, is no easy matter.
"I am still not sure one way or another," said Sainz. "It's still something that I'm discussing with my team, and brainstorming, and obviously I need a couple of days back at home.
"It is a bit of a lottery, or a coin toss, to see who’s going to be quicker in '26 given that the regulations are so different."
Sainz is also key to the wider driver market, with others waiting to see where he goes.
"Carlos is the cork in the bottle," said Haas's Kevin Magnussen, who also looks likely to be on the move at the end of the year.
"A lot of guys are waiting for him to make a move. Then eventually all the other pieces of the puzzle will fall. That's the truth of that."
Sauber have already announced Haas's Nico Hulkenberg as one of their drivers while Williams have Alex Albon signed up on a multi-year deal.
Sauber's Valtteri Bottas and China's Zhou Guanyu could be looking for seats while American Logan Sargeant is not expected to retain his place at Williams.
Alpine's Esteban Ocon is also looking for a drive and waiting on Sainz after Renault-owned Alpine announced he would be leaving.
