"I'm still trying to get a good performance from us to convince them (to stay)," Honda's Yusuke Hasegawa said on Sunday. "But I'm not sure it will be enough."
Indeed, the rhetoric from bosses Zak Brown and Eric Boullier indicates that the Woking team's patience is definitely up.
"McLaren has always reached its targets. Honda have never reached theirs," Boullier declared.
But although believed willing to take a $100 million per year hit by cancelling its Honda sponsorship, McLaren cannot simply quit the deal.
That's because it needs an engine supplier to switch to -- and Mercedes, Ferrari and Renault are all fully-subscribed with three partner teams apiece.
So McLaren is trying to convince Toro Rosso and its owner Red Bull to give up the Faenza team's customer Renault deal in order to keep Honda in F1.
"The situation is complicated because it's not just about McLaren," Boullier said.
"We also need to consider what is best for the whole of formula one. All parties to the negotiations understand this. I cannot tell you any more about it."
McLaren executive Zak Brown said: "The ideal scenario is where everyone is smiling at the end.
"But to get there Toro Rosso has to play along.
"We need to know what we are doing and where we are going, because we're now in a timeframe that affects the design of the car for next year," he added.
Renault advisor Alain Prost said of the French supplier: "We are ready.
"But first, Toro Rosso, McLaren and Honda have to agree," he told Bild newspaper.