Despite his on and off-track clashes with teammate Esteban Ocon, the Mexican driver had said recently he hoped his future would be decided by Monza.
Now, the parties are targeting Singapore in two weeks.
“There’s not much left to agree with Checo (continuing),” sporting boss Otmar Szafnauer said.
As for the long delay in announcing the deal, however, he explained: “I don’t think it’s a secret that since he (Perez) started racing, he has had Mexican sponsors.
“So the difficult thing is that with Checo you almost have to do two contracts,” Szafnauer added.
“We agree completely with Checo, but we must also look to the side with his supporters.”
However, the 2018 ‘silly season’ remains in a state of flux, particularly with Perez and Ocon at loggerheads and McLaren and Toro Rosso yet to even confirm their engine suppliers.
It means someone like the Mercedes-backed Pascal Wehrlein is having to wait for now.
“We are looking for opportunities (for Wehrlein),” Mercedes team chairman Niki Lauda told Speed Week, “but nothing is decided yet.
“It changes every day, because no one knows if Toro Rosso will have a different engine or what is going on with Force India.
“So for the moment, everything is still open,” Lauda added.