Renault chief Cyril Abiteboul has warned Red Bull a switch to Honda would cost it the chance of winning the world championship before 2021.
Red Bull has two options for next year: sign a new deal with Renault or switch to Honda, which has powered junior team Toro Rosso this year. Honda has enjoyed improved fortunes this season but has been a long way off the pace since returning to the grid in 2015.
Both manufacturers arrived in Canada with engine upgrades and Red Bull will be able to compare the data from both. Abiteboul says Red Bull should be very careful when making its final decision.
"I understand what they are looking to get," Abiteboul told Sky Sports. "They are looking to the technical and commercial side, because it is clearly different remaining a customer and partner of Renault versus becoming a works team with Honda. It is very different and I appreciate that.
"But frankly, as far as I am concerned, they have a chance with us to become world champion again. I cannot say for Honda.
"With what they have now, what is coming in the pipeline, and their car which is clearly a great car, maybe the greatest out there, they have the chance to be world champion again within the next two years."
Abiteboul pointed out that the two wins Red Bull and Daniel Ricciardo have claimed this year show the potential of the entire package.
"It is a complex decision for them and for us. Maybe it is my emotional side. I have been working 12 years of pulling my hairs with Christian [Horner] and Helmut [Marko], and I don't want to lose any of that.
"But frankly, in the construction of the Renault team, I think it is still interesting to get their benchmarking capacity. We know where we need to work based on what they are doing.
"They have showed that a Renault engine can win races in straight conditions, so that is a good sign of what we are doing, where we are progressing and where we need to progress."
With the races in Canada and France taking place on power-sensitive circuits, Red Bull boss Christian Horner hopes Red Bull will be in a position to make a decision at its home grand prix in Austria.
"We are at a crucial part of the season where the data we take out of this weekend is going to be fundamental to our decision-making for the future," Horner said. "Probably in an ideal world we would want to see two samples of that, here and in France, but certainly by the Austrian race we would have made a decision by then.
"We want the best engine that gives us the most competitive chances going forward. Whether that is a Renault or a Honda that is the decision we've got to make in the next week or so."