McLaren are hoping the MP4-19B will rescue their season

The team will decide whether to give the new MP4-19B its race debut at the French Grand Prix on 4 July after this week's test at Jerez in Spain.

McLaren test driver Pedro de la Rosa set the fastest time on Wednesday, nearly a second quicker than Williams test driver Marc Gene.

McLaren's reserve driver Alexander Wurz was third fastest at the test.

The Austrian's lap of one minite 18.123 was just over a second slower than De la Rosa's pace-setting1:17.057. Gene managed 1:17.951.

McLaren hope the MP4-19B will turn around their fortunes in what has so far been a disastrous season.

Their current car, the MP4-19, has proved both slow and unreliable.

The 19B is heavily revised, with a new chassis and fundamentally redesigned aerodynamics and extra features aimed at reducing the fragility of its Mercedes engine.

McLaren will make its decision regarding the French Grand Prix after weighing up the performance and reliability of the new car in Jerez.

BAR's Takuma Sato was fourth with a 1:18.540 lap, followed by Toyota test driver Ricardo Zonta, BAR tester Anthony Davidson and Williams' other test driver Antonio Pizzonia.