How the Renault and Honda engines compare to each other in Montreal next week could determine Red Bull Racing's 2019 power unit choice.

Renault's Cyril Abiteboul has been asking the Milton Keynes-based outfit for clarity sooner rather than later on its future engine plans, but team boss Christian Horner insists Red Bull will continue to weigh its options until the end of June or early July.

"It will be a month or so. End of June, beginning of July. It's the time-frame we've always talked about," said Horner.

"We want to compare the two engines in Canada," added Horner, amid reports both Renault and Honda are planning upgraded units for the seventh round of the world championship.

"We'll get small updates in Montreal but we need to get the most out of them. It's very important to us."

Renault's power unit has reduced its deficit to its Mercedes and Ferrari rivals, but the French manufacturer has still not offered its customers the compelling qualifying modes enjoyed by its main competitors and necessary to fight for pole.

Horner believes that's the only thing keeping Red Bull from consistently challenging for race wins.

"If I'm not mistaken, in the last six races the five fastest laps were ours," he said.

"If we get more power in the last qualifying session, there will be nothing stopping us from making the lives of Mercedes and Ferrari very difficult."

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