(CNN) -- World champion Jenson Button fired a warning to his 2010 title rivals that he will be just as quick with new team McLaren after setting the fastest time of the pre-season testing sessions in Jerez.
The British driver, who left Brawn ahead of the manufacturers' champions takeover by Mercedes following the capture of his maiden drivers' crown, ended the eight days at the Spanish circuit top of the timesheets on Saturday following a best effort of one minute 18.871 seconds.
That run put the 30-year-old ahead of the 1:19.299 set by Red Bull's Mark Webber on Friday and the 1:19.583 recorded by new McLaren teammate and 2008 world champion Lewis Hamilton last week.
McLaren reported on their Web site that Button was "very comfortable and confident in the car" as he completed 108 laps in his third test with the team ahead of the final sessions in Barcelona next week.
"Both drivers will spend alternate days in the car evaluating the new bodywork and aerodynamic components ahead of the season-opener in Bahrain on March 14," McLaren said.
Renault's new signing Robert Kubica was second fastest in Saturday's sessions, completing 117 laps in long runs in the R30.
Sauber's Kamui Kobayashi was third quickest over a similar distance ahead of Force India's Vitantonio Liuzzi and Nico Rosberg in a Mercedes after the German took over from Michael Schumacher.
Ferrari's Fernando Alonso was sixth, while Webber was back in eighth after his RB6 could manage only 88 laps after an engine failure.
Meanwhile, struggling new team Campos hope to be on the grid in Bahrain after confirming that shareholder Jose Ramon Carabante has now taken a controlling stake.
The Spaniard has appointed former Force India boss Colin Kolles as team principal of an outfit which has just one confirmed driver, Bruno Senna.
"I would like to thank Bernie Ecclestone, who worked tremendously to support our efforts to keep the team viable," Carabante told F1's official Web site.
"The whole rescue operation has been a race against time with the goal of always having the team run two competitive cars at the first Grand Prix of the F1 season.
"We have a lot of hard work still ahead of us but we are excited about making our F1 debut and looking forward to a competitive season."