Multiple sources are reporting that, in Singapore, the Spaniard will sign a contract to complete his switch from the junior Red Bull team to Renault.
It appears to be the move that completes the complex divorce saga between McLaren and Honda, with the British team switching to Renault power for 2018 and Toro Rosso signing up with Honda.
However, Sainz is not confirming his impending move.
"Red Bull does its best for my career and so whatever they decide, I will accept it," he told Marca during a sponsor event at the weekend.
"It is difficult for me because what I say may please one person and displease another, so I prefer to say nothing.
"All I know is that there are many people in Toro Rosso that I want to think for making me the driver I am today."
Asked if a conclusion to the entire McLaren-Honda-Renault-Toro Rosso saga is now imminent, he answered: "I don't know.
"But I think for the sake of the teams involved, they are going to have to decide sooner rather than later, because [preparation for] 2018 is already here," Sainz told EFE news agency.
Germany's Auto Bild said that the transfer fee agreed between Red Bull and Renault for Sainz is €8m (£6m).
The publication said that Sainz, 22, had a seat fitting at Renault's Enstone factory last week.