- Sebastian Vettel sets fastest time in free practice for Sunday's Singapore Grand Prix
- Vettel two-tenths of a second quicker than closest title rival Fernando Alonso of Spain
- Germany's Vettel can clinch world championship with victory in the night race
- Lewis Hamiton of Britain third quickest in his McLaren
Championship leader Sebastian Vettel continued his domination of the Formula One season by setting the fastest time in Friday's practice for this weekend's Singapore Grand Prix.
The Red Bull star can clinch his second straight F1 title with victory in Sunday's night race and set about the task by clocking the best lap of one minute 46.374 seconds in the second session.
Closest rival Fernando Alonso took second fastest, ahead of McLaren's Lewis Hamilton, who was quickest in the morning runs. Alonso's Ferrari teammate Felipe Massa was fourth best.
Germany's Vettel can become the youngest ever two-time champion at 24 if he wins and other rivals finish off the podium, but he played down his early success.
"I think it looked pretty tight. It depends where and when and who was out, we have to wait and see," he told AFP.
"I didn't have as much time as you to look at the times so I was busy when I was on the track, but surely Ferrari looked quite competitive," he added.
Vettel's teammate Mark Webber was fifth best in the second Red Bull ahead of seven-time champion Michael Schumacher of Mercedes, who was fully two seconds off Vettel's pace.
Jenson Button was back in 10th fastest after brake problems in the McLaren and he almost lost control as he tackled Turn 14 before calling it a day.
Vettel is bidding for his ninth win of the season but will have to tackle temperatures of well over 30 degrees centigrade and high humidity which could affect tire choice.