Sebastien Buemi increased his chances of racing for Toro Rosso by outpacing Sebastien Bourdais in testing at Jerez.

The 19-year-old Swiss driver, who has long been touted for one of the two vacant seats for 2009, comfortably topped the timesheets at the end of the first of three days at the Spanish circuit.

With little to be read into the testing times of the nine drivers due to each of the six teams on track running varying development programmes, Buemi at least outshone teammate Bourdais.

Buemi covered 91 laps, with his fastest a one minute 18.742 secs in a car replicating the expected downforce levels ahead of the new aero rules for next year, with Bourdais second quickest, but half a second down.

The McLarens of Gary Paffett and Pedro de la Rosa, evaluating the KERS boost levels and set-up respectively, were third and fourth, separated by just three hundredths of a second.

Kimi Raikkonen, returning to the cockpit of his Ferrari for the first time in a month, was fifth after working on set-up and long-distance evaluation of the car's engine.

Nick Heidfeld was sixth for BMW Sauber as he looked at suspension and aero, with test driver Christian Klien last of the nine after only completing 15 laps due to an engine issue.

Kazuki Nakajima and Nelson Piquet for Renault, the latter running with slick tyres and simulating a 2009 set-up, were seventh and eighth.