Vettel says Mercedes doing their usual sandbagging

Sebastian Vettel is still viewing Mercedes as a serious threat for pole position in Singapore, despite comfortably topping the overall practice timesheets on Friday.

The Red Bull driver, who finished 0.604 seconds clear of team-mate Mark Webber and over a second faster than Mercedes duo Nico Rosberg and Lewis Hamilton, says although his pace was a surprise, the Silver Arrows will be "very strong" in qualifying.

"It was quite busy; it's pretty hot out there, good fun and a nice place, but for all of us it's quite hard work," Vettel began after his day behind the wheel. "The time we set was a surprise today. I got a good lap in, but I don't think it's completely representative.

"We seem to be quick, but I think Mercedes will be very strong in qualifying tomorrow."

Outgoing teammate Webber wound up second fastest in both 90 minute sessions, the Australian admitting that he has "work to do" on both his long and short runs.