BARCELONA, May 12 (Reuters) - Red Bull's Formula One world champion Sebastian Vettel wrapped up practice for the Spanish Grand Prix in ominous form on Saturday with the fastest time of the final session.
The 24-year-old German, winner at the Circuit de Catalunya last season, lapped in bright sunshine with a best time of one minute 23.168 after being second in both Friday stints.
Championship leader Vettel is chasing his second win in a row, after his victory in Bahrain last month, and his team's third in succession in Barcelona.
Australian Mark Webber won the 2010 race, traditionally one of the most predictable on the calendar, from pole.
In the past 21 years only one driver, Michael Schumacher from third place with Ferrari in 1996, has ever won at the circuit without being on the front row of the grid.
Webber, on pole for the past two years, was fourth fastest behind second-placed Venezuelan Pastor Maldonado in a Williams and Sauber's Japanese Kamui Kobayashi.
Maldonado had looked like taking the honours until Vettel popped in a quick lap in the final seconds, pushing him off the top of the timing screens.
Ferrari's Home favourite Fernando Alonso was sixth fastest, behind Mexican Sergio Perez in the Ferrari-powered Sauber, in an upgraded car he hopes will put him among the contenders in Sunday's race.
McLaren's Jenson Button, fastest on Friday, and Lewis Hamilton were eighth and 16th respectively although the latter could have been quickest of all had he not been blocked on a late quick lap on soft tyres.
Frenchman Romain Grosjean failed to set a lap due to a fuel pressure problem with his Lotus.
Indian Narain Karthikeyan did finally get out of the garages in the HRT, however, and completed 24 laps - more than anyone else - after doing none on Friday. (Editing by John O'Brien)