BRNO, August 15, 2008 (AFP) - Reigning world champion Casey Stoner clocked up the fastest time in free practice here on Friday to send a message to his rivals ahead of Sunday's Czech Republic Grand Prix.

The Australian Ducati rider posted 1min 57.231sec which was 0.179sec in front of perennial foe Italy's Valentino Rossi, on a Yamaha.

Fellow Italian Loris Capirossi, on a Suzuki, was third fastest, coming in 0.769sec behind.

Rossi leads the drivers' championship on 212 points with Stoner trailing by 25 points.

Honda rider Dani Pedrosa, third in the standings, had a poor practice run, posting a disappointing 16th fastest time.