Sainz has been lent out by Red Bull to the Renault team for this season, and can be called back for 2019 if the team loses Daniel Ricciardo to a rival outfit.

With Ricciardo's future unlikely to be settled until the summer, it means Renault is in a tricky spot because it is not totally in control of what happens with its line-up.

Despite that uncertainty, Renault F1 managing director Cyril Abiteboul has told Motorsport.com that it is already discussing a long-term plan with Sainz.

"We have in my opinion still two great drivers, but obviously we have a particular situation with Carlos, which is a contract where we are exposed for next year, and we knew that since day one," said Abiteboul.

"That's why we need to start thinking way in advance about what could be the situation. And frankly, that is why we have already started discussion with Carlos about longer term, about what can happen beyond this year, accepting that it's not completely in his hands nor our hands.

"[It is] not a super comfortable situation to be in, but we need to accept that we are still playing catch up on many areas and one of the areas is also driver market, where we still need to try to be more in control of our future and of our destiny."

When asked by Motorsport.com about his contract talks with Renault, Sainz said: "I think both [Renault and me] are happy with the situation. I am very happy with Renault, I feel privileged to be part of this brand and it seems that Renault is also interested in being able to continue with me in the future.

"But I think it is still too early to talk about the future. We are in the fourth race and it is not yet time to talk about 2019."

Abiteboul said the team was not in a situation yet where its junior drivers like Jack Aitken were ready for the step up to F1, nor was the outfit strong enough to attract regular race winners like Daniel Ricciardo.

"We are interested in talented drivers, and Ricciardo is a talented driver," explained Abiteboul, when asked about interest in the Australian.

"I think Daniel Ricciardo is very well positioned to have a very clear understanding about where we are strong, where we can be weak. And I am talking about the engine, because obviously he is using a Renault engine, which can be good and some time can be wrong.

"If we want to seduce drivers like Ricciardo – maybe Ricciardo, but maybe other drivers – the first thing that we need to do is to to get our stuff right. And if we manage to build the best chassis/engine package, I am pretty sure that we can attract, because we can show that we are serious about our ambitions, someone like Ricciardo.

"But the first thing that we need to do for Daniel is to fix… not fix, because it's not broken, but to make sure that we are in complete control of the engine situation."

While Abiteboul is already pushing Red Bull to make a decision on its engine plans for 2019, as the Milton Keynes-based outfit courts Honda, he is also eager for it to make a call on whether or not it wants Sainz back.

"Maybe we cannot control everything, but at least we need to have visibility on the future," he said. "And that is why I am also acting to speed things up with Red Bull on the engine side, and that will be the same also on the drivers' side.

"We need to be fixed about our plans as soon as possible, bearing in mind that we can't control everything."

Additional reporting by Jose Carlos de Celis