Red Bull fastest in Singapore practice

Red Bull threw down the gauntlet to its Formula One championship rivals by setting the fastest times in today's practice for the Singapore Grand Prix.

Sebastian Vettel set an impressive time of 1 minute, 46.660 seconds around the Marina Bay circuit in the second practice session - six tenths of a second clear of teammate Mark Webber and a full second faster than third-fastest Jenson Button of McLaren.

Ferrari's Fernando Alonso's session was cut short after he took an escape road and couldn't restart the car. Alonso had looked set to better Vettel's time on that lap, but ended the session fourth fastest.

McLaren's Lewis Hamilton was fifth, with the five top drivers in the championship standings setting the five fastest times in the session - setting the stage for a hard-fought qualifying on Saturday.

The opening practice session was affected by rain. Although the showers stopped almost two hours before the session and two support races were staged between the rain and opening F1 practice, the track remained wet enough for all but the final 20 minutes of practice to be done on intermediate tires.

The slow-drying street circuit faces the prospect of either Saturday's qualifying or Sunday's race starting on a damp track, given afternoon rain was forecast for both days.

Webber was fastest in that opening session, but little could be read into the performance because of the lack of laps on slick tires.

The showing of Webber and Vettel in both sessions dashed the hopes of both McLaren and Ferrari that Red Bull's advantage this season on high downforce tracks had been negated by new rules that limit the cars' floor flexibility. The new regulations came into effect since the Monaco and Hungary races, which are staged on similarly twisty tracks to Singapore.

Force India's Adrian Sutil snapped his front suspension when going too hard over the kerbs and Renault's Robert Kubica also had his second session limited by a mechanical issue.