Christian Horner is expecting Mercedes to be fighting at the front for at least the next two Grands Prix, at circuits that the Red Bull boss fears will not suit the RB18.
Formula 1 will return to Europe for the British Grand Prix next month before a run of races that will take them through France, Austria and Hungary before the summer break.
Red Bull head back to their Milton-Keynes base, just 12 miles from Silverstone, having made it six Grand Prix wins on the bounce.
However, Horner fears races in Britain and France will be their most challenging yet, with both Mercedes and Ferrari expected to be at their very best on smooth, high-speed venues.
"I think Mercedes will be strong at Silverstone and I don't see any reason why they wouldn't be at Paul Ricard," he said, speaking to media including RacingNews365.com.
"I think Ferrari will be quick at Silverstone as well. It could be more of a challenging circuit for us, just due to the nature of its layout.
"It's incredible that we've put a run of six race victories together but Silverstone could well be the most challenging yet."
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Red Bull within five race wins of historic record
Red Bull's mighty run of results is the second-longest winning run in their history, bettered only by Sebastian Vettel's incredible nine-straight wins as he romped to a fourth title in 2013.
McLaren holds the all-time record for most consecutive wins, having won 11 races on the bounce back in 1988 with their all-conquering MP4/4.
"I would love to continue winning but with every race it gets harder," continued Horner, who does not have his eyes on the record.
"When you think of the swing in the championship from where we left Australia to where we are today, it just shows how quickly things can move.
"I think Max [Verstappen] has hit a purple patch of form. The car was a bit more to his liking now as well."
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