By John O'Brien
SINGAPORE (Reuters) - Ferrari and Red Bull appear poised to claim a first pole position of the season at the Singapore Grand Prix on Saturday after both teams easily outpaced Mercedes in the final free practice session ahead of qualifying.
Four-time world champion Sebastian Vettel was in supreme form around the Marina Bay Street Circuit, lapping almost half a second faster than his Ferrari team mate Kimi Raikkonen to top the timesheets in one minute, 45.682.
The Red Bulls of Daniil Kvyat and Daniel Ricciardo were close behind as championship leader Lewis Hamilton and his Mercedes team mate Nico Rosberg toiled more than a second off the pace as the sun set over Singapore.
The lack of pace will worry the German outfit, whose superior engine lacks a clear advantage around the tight, 23-turn circuit with the hot and humid conditions set to scupper the team's hopes of securing a 13th pole in as many races.
The championship leaders have two hours to try and eat into the time gap ahead of qualifying but on the evidence of Friday's second practice and the hour-long session on Saturday, Ferrari and Red Bull could well lock out the front two rows of the grid.
Starting the final session in twilight on a muggy yet clear evening, the main contenders waited 15 minutes before venturing out on to the circuit and when they did, several ran wide at Turn Seven, the fastest part of the circuit.
Shortly before the midway point of the session, Vettel emphasized his speed by putting in the cleanest lap of the weekend so far on the more durable soft tyres, immediately roaring to the top of the timesheets by almost a second.
As the track cleared in the closing stages, the final 10 minutes became a shootout for most of the leading contenders, who fitted the quicker super soft tyres to attempt some fast laps ahead of qualifying as the sun set over Singapore.
Ricciardo was the first to leapfrog Vettel's time set on the slower tyres but he was soon passed by Raikkonen and Kvyat before Vettel crossed the line almost half a second quicker than the rest.
Hamilton and Rosberg, meanwhile, were unable to make any inroads into the times set by the leading quartet and may be opting for a damage limitation exercise in Sunday's demanding 61-lap race around the 5.065 km layout.
With seven rounds remaining, Hamilton leads Rosberg by 53 points with Vettel in third place, 21 points adrift of his fellow German.
(Editing by Amlan Chakraborty)