A team spokesman said: "Although we had hoped to introduce PU2 this weekend, a quality issue means that this has now been delayed by one race".
Like Mercedes, both Red Bull and Ferrari are expected to use new engines, but Red Bull technical boss Adrian Newey downplayed expectations, notably because Monaco victor Daniel Ricciardo faces grid penalties for other technical power-unit changes.
"Montreal is a venue that nearly always delivers an action-packed race", said Mercedes team boss Toto Wolff.
"So all Mercedes-powered cars will be running PU1 again this weekend, too, before the new units are available in France".
The Scuderia could also face a reduced threat from Red Bull as their vehicle is likely to be less suited on the long straights, though will be strong in the many heavy braking zones.
Rival engine manufacturers Honda and Renault are pressing ahead with planned power-unit upgrades this weekend.
The video, published on Tuesday, June 5, pages Scuderia Ferrari, says: "We are ready to Montreal".
"It's a great track and a real test for the driver and the vehicle".
Montreal has also seen of the craziest races in recent history from Hamilton's first win in 2007 to Robert Kubica coming back from a massive crash that year to claim his first F1 win for BMW 12 months later.
But others have also found the track to their liking including two of Hamilton's biggest challengers.
In the morning session, Williams driver Sergey Sirotkin spun and hit a wall, but was able to continue.
That emotionally charged weekend was capped off by a sixth win in Canada. "For us, it's a tough one to take, but there are lots of lessons to be learned so we can come back stronger next time".
The Silver Arrows now lead both the drivers and constructors championships after six races.
The team's struggles with the "hyper-soft" tyre in Monte Carlo undermined them in qualifying, but their strategic approach enabled Hamilton to finish third and extend his record run of points-scoring races to 31.
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