McLaren are considering "all possible scenarios" amid rumours that the British team are on the cusp of dumping works engine partner Honda.
Team executive Zak Brown this week gave an explosive interview indicating McLaren's patience is up, while boss Eric Boullier questioned Honda's "commitment".
Asked how he responds, Honda F1 chief Yusuke Hasegawa said in Montreal: "I don't respond."
"It is very difficult but it is very unfortunate that we can't convince them that we can do that," said the Japanese, when told that McLaren seem to have lost faith that Honda can turn it around.
Also in the Circuit Gilles Villeneuve paddock, Brown said that Honda not delivering on a pledge to upgrade its engine by Canada had left McLaren more than disappointed.
"This is not acceptable," he said.
"We cannot allow a repeat of this in 2018. In preparing for next season, we need a guarantee that we are able to achieve better results.
"Our company's executive committee believes McLaren's interests are paramount, and it is clear that we can no longer remain uncompetitive.
"We have already said that we consider all possible scenarios, but there is no need to make any decisions today. But I think we can say that it should be taken around the summer break."
Previously, former team supremo Ron Dennis said that McLaren can only win a title in works collaboration with a carmaker, but Brown has a different view.
When asked about the fact that Honda actually sponsors McLaren, while switching to Mercedes or Renault will mean a bill for the team, Brown said: "It is a commercial decision.
"No matter how good the deal is with Honda, eventually we begin to incur serious financial losses in the form of not getting the [F1] payments. And we have lost several sponsors that moved on to other teams.
"Clearly McLaren is upset and Honda is upset, but in this situation you need to be open and honest. We cannot continue to insist that everything is fine."
McLaren's disappointing start to the season has seen them fail to register any points so far.
