SINGAPORE (AFP) - Lewis Hamilton blamed the "weird" performance of his tyres on Saturday, as his run of seven straight pole positions came crashing to a halt at the Singapore Grand Prix.

The Mercedes championship leader was never in the running in qualifying as he came in fifth, 1.4 seconds slower than pole-sitter Sebastian Vettel of Ferrari.

Afterwards, Hamilton, who missed out on equalling Ayrton Senna's record of eight consecutive poles, said his tyres weren't performing as expected - but couldn't explain why.

"It's so weird: you heat them up the same as everyone else, you do your warm-up lap the same as everyone else," he told Sky Sports.

"Then you finish your lap, which you think will be okay grip and then you see someone else a second up the road. So it's very strange."

Hamilton also admitted that Mercedes could struggle in Sunday's race, with his team-mate Nico Rosberg starting alongside him on the grid in sixth.

"The goal's still to win the race, but it's very hard to overtake here and the others, particularly the Red Bulls, were incredibly quick through the long runs," Hamilton said.

"It is what it is. We'll fight as hard as we can, but I doubt we'll find something between now and tomorrow. But if we do, great."