Hamilton admits Ferrari and Red Bull in 'place of their own'
The 37-year-old Briton, without a win after 11 races this year, will line up Sunday for his 300th race knowing he faces a struggle to close a significant performance deficit.
Charles Leclerc of Ferrari, world champion Max Verstappen and his Red Bull teammate Sergio Perez all qualified ahead of Hamilton.
"They are in a place of their own," said Mercedes driver Hamilton.
"But we are still here and everyone behind us is struggling so we just keep on fighting."
He added that he was pleased to have recovered from a shaky start to the weekend when he missed opening practice –- handing his car to reserve driver Nyck de Vries for a mandatory session -– and had to "play catch-up".
"To be honest, I'm really happy with my qualifying. My last lap was great.
"Overall, I am not sure why the gap has got bigger. They are kind of in their own league in that respect."
He said that anticipation of the latest updates package bringing a quantum leap in performance was misplaced.
"When we said we have updates, we brought the tiniest thing. It could be half a tenth of half a tenth if it was perfect," he said.
"Last race, we were three or four tenths off, so this weekend I thought we'd maybe be two-tenths off, but then we've been a second back all weekend."
Hamilton's team-mate George Russell, who was out-qualified by friend and fellow Briton Lando Norris of McLaren, ended up sixth and said he had made a mistake.
"As a team, we're probably a bit further away from what we hoped and probably expected, especially after yesterday. I made a mistake on my last lap.
"It's not the end of the world. I think the gap is more concerning than the finishing order."