F1: Button on top for McLaren in final practice

SAO PAULO (AFP) - Jenson Button kept McLaren on top of the time-sheets when he clocked the fastest lap in Saturday morning's third and final free practice session ahead of this weekend's title showdown Brazilian Grand Prix.

The 32-year-old Briton took over from team-mate and compatriot Lewis Hamilton, who had topped the times in both sessions on Friday as hot and humid weather replaced the blue skies and McLaren continued to upstage the championship protagonists.

Defending champion Germany's Sebastian Vettel, who needs to finish fourth or better to be certain of becoming the youngest triple champion in Formula One hitory, was second fastest ahead of his Red Bull team-mate Australian Mark Webber.

Button's McLaren team-mate Hamilton was fourth fastest in a closely-fought session that saw the top four drivers separated by only two-tenths of a second.