Sep.25 (GMM) Lewis Hamilton agrees with his chief championship rival Felipe Massa that qualifying for this weekend's Singapore night race will be crucial.

"I've never driven on the but it'll be even more difficult to overtake compared to Valencia," Brazilian Massa, who drives for Ferrari, said.

McLaren's Hamilton, one point ahead of Massa in the drivers' standings with four races to go, agrees.

"Overtaking is going to be very tricky, as it is at all street circuits," the Briton said on Thursday. "There will be a little bit less overtaking than at the other circuits we have.

"It's going to come down to qualifying."

On a dry track, Ferrari and McLaren's respective single-seaters are very closely matched for pace, and both teams now feature second drivers that are effectively racing in support.

F1 chief executive Bernie Ecclestone thinks Sunday's race is key to the championship battle.

"Whoever wins this, where it's Hamilton or Massa, will probably be the champion," he told the local Straits Times.