Rumours are growing by the day that the works McLaren-Honda partnership is now definitely doomed.

It seems that the final straw for the British team was Montreal, where Honda failed to deliver on a promise to upgrade its unreliable and underperforming power unit.

Then, Fernando Alonso retired within sight of the team's first point of 2017.

"It's difficult to find the words to express our disappointment, our frustration and our sadness," said team boss Eric Boullier.

"It's simply and absolutely not good enough."

Once a believer in Honda's potential, key team driver Alonso's message in Canada was that while McLaren are ready to win, the Japanese marque may never be.

"After 16 years, it doesn't change my life to win a point or not, but we have to start scoring for the work that the mechanics do day and night, changing many engines," he said.

After the new engine did not arrive in Montreal, it remains unclear whether it will appear in time for Baku next weekend.

"I do not have information about the improvement of the engine," the Spaniard told Movistar. "I do not work for Honda and I'm not an engine designer."

Alonso is also quoted by Blick newspaper as saying: "I am of course frustrated, but especially at this time for McLaren, who always give me a top car which is then attacked by everyone on the straight."

The 35-year-old's best finish of the 2017 campaign so far was 12th at the Spanish Grand Prix.