Sebastian Vettel offered up hope Red Bull's Formula One world title challenge is far from over this season.

Two alternator failures in Valencia and last time out in Italy have seriously undermined his title hopes but the 24-year-old German goes into this weekend's Singapore Grand Prix 39 points adrift of leader Fernando Alonso, with Lewis Hamilton and Kimi Raikkonen one and two points ahead of him respectively.

But after a tough time in the last two races, with the Red Bull found to be lacking in pace after opting for a wrong choice of wing, Vettel at least finished top of the first practice session.

A thunderstorm earlier in the day swiftly brought an end to practice for one of the support events, the Ferrari Challenge, and the Marina Bay Street Circuit was still wet when GP2 practice began

But come the opening 90-minute F1 session, the 23-corner track over five kilometres had virtually dried out, unsurprising given the 28 degree heat, even as daylight moved to dusk and into night.

Come the conclusion Vettel and Hamilton were in a class of two out in front, the former finishing just 0.049secs ahead of the Briton.

As for the rest, team-mate Jenson Button led the way, albeit almost nine tenths of a second adrift, followed by Alonso, the Spaniard the only other driver to finish within a second of Vettel at 0.959secs.

Williams' Pastor Maldonado, Mark Webber in his Red Bull and the Force India of Nico Hulkenberg were fifth, sixth and seventh on the time sheet, the trio covered by 0.082secs.

Paul Di Resta had to contend with being behind team-mate Hulkenberg by nearly three tenths of a second, with Toro Rosso's Daniel Ricciardo and Sergio Perez in his Sauber both 1.7secs off the pace as the duo rounded out the top 10.