Renault supply engines to Red Bull, Toro Rosso and their own factory team

Renault say they are "open" to supplying engines to McLaren next season "but not at any cost".

McLaren are exploring splitting with partner Honda after three years plagued by poor reliability and performance.

Renault emerged as their only remaining option if they can negotiate an exit from their contract, after Mercedes and Ferrari rejected their approaches.

Renault F1 boss Cyril Abiteboul said a McLaren deal was appealing but not if it compromised the company's own team.

"I like the idea of working with great teams and McLaren is a great team but not at any cost," he said.

"I'm not talking about the price. Clearly one thing I do not want is to jeopardise what we are building for the Renault team, which has to be our main focus."

The Frenchman said he was "not really keen on" the idea of supplying a fourth team and that doing so "would not be without huge concessions on the sort of service we could deliver to a fourth team as long as Renault is concerned".

He added: "It's quite obvious we do have some difficulty this year with reliability and adding another customer is clearly not going to go in the right direction even if our assumption next year is that we will become more reliable. It is becoming very late to add a customer and we have no such confirmation."

The number of grid places lost through penalties of all the engine suppliers in 2017. Going all right for Mercedes, Ferrari and Renault...

Last month, McLaren were working on a deal whereby they and Red Bull's junior team Toro Rosso effectively swapped engines next year, with Toro Rosso using Honda and McLaren Renault.

Those negotiations have stalled and are waiting on a resolution of McLaren's position with Honda.

One senior source close to the situation said he "wouldn't be surprised if when everything shakes out everyone ends up staying where they are".

Abiteboul said: "If we were to stick with that same number of customers - three customers - we are open to some discussion."

He pointed out that if Honda made the decision to pull out of F1 completely, one of the remaining engine manufacturers would be under an obligation to supply McLaren.

McLaren executive director Zak Brown said he would be "very supportive" of Honda joining forces with Toro Rosso.