Hamilton held off the challenge of both drivers to clinch pole position, and although he said that it will be possible to turn it into a win, the challenge ahead remains "very hard".
"I think it is going to be very hard," he told Autosport. "The Red Bulls have made a step this weekend, and I think a lot of teams have made a step forwards.
"Webber said to me that the tyres seemed to work on his car, so I think perhaps they have potentially gained a bigger advantage than we have with this switch of tyres. His long run was very strong the other day, so I anticipate that they will both be strong tomorrow - but of course it would help if we could get into Turn 1 in the lead and hold them behind.
"We still have degradation issues, so it is not something that we have completely cured, but I don't think it is impossible."
Vettel qualified second and Webber third for Sunday's race.