F1: Rosberg quickest in final practice

Mercedes continued its dominance of Formula 1 as Nico Rosberg topped the third practice session for the Spanish Grand Prix ahead of his teammate Lewis Hamilton.

Qualifying will most likely be another personal duel between the two Silver Arrows machines. They were split by 0.869 second in Saturday morning practice. Local hero Fernando Alonso was third quickest in his Ferrari, more than 1.3sec behind Rosberg and just fractionally ahead of Felipe Massa's Williams.

Frenchman Romain Grosjean was fifth quickest for Lotus ahead of Kevin Magnussen (McLaren), Daniel Ricciardo (Red Bull) and the other McLaren of Jenson Button.

Pastor Maldonado was ninth quickest in the second Lotus, while Sebastian Vettel made up for the time he lost on Friday by completing 20 laps in his Red Bull and finishing with the 10th-fastest time.

At the beginning of the hour the Ferraris set the early pace, with firstly Kimi Raikkonen, then his teammate Alonso going fastest on the hard tires in the first 20 minutes.

As the half-hour mark approached the Mercedes drivers emerged from the pits and started lighting up the times. Rosberg was first to post the quickest time, over a second faster than Alonso's Ferrari.

Rosberg and his teammate Hamilton then traded fastest lap times at the top of the order, but it was clear that a number of drivers continued to struggle with the low grip on a dry but overcast day in Barcelona.

Several drivers, including the spectacular Alonso, battled with rear grip issues and once again Max Chilton's session ended in the gravel trap, this time after he locked up his front left heading into Turn 5 and slid wide into the gravel on the outside of the corner.

Kamui Kobayashi also had a late off-track excursion in his Caterham but was able to continue unharmed.