SINGAPORE (Reuters) - Ferrari’s Kimi Raikkonen set the fastest practice time for the Singapore Grand Prix on Friday but the Finn’s team mate Sebastian Vettel suffered a frustrating start to the weekend in his bid to overhaul championship leader Lewis Hamilton.

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Hamilton opened a 30-point cushion over Vettel with a surprise win in Monza two weeks ago and while Ferrari are regarded as having a superior car, the Briton set the second-fastest time of the day just 0.011 seconds back in his Mercedes.

Vettel has been criticized for dropping points due to some poor tactical driving this season but there was little he could do looking on from the Ferrari garage after his car suffered a radiator fluid leak midway through the second practice session.

Raikkonen lapped the 5.063 km Marina Bay Street Circuit in 1:38.699 seconds, with Hamilton just behind as the rejuvenated Red Bulls of Max Verstappen and Daniel Ricciardo finished third and fourth respectively half a second further back.

Vettel’s troubles began during the frantic middle sector of the second session as drivers looked to set their fastest laps on the high-grip hypersoft tires before switching to slower compounds for race simulations.

The German was on course to challenge Raikkonen and Hamilton’s best times before he clipped the wall on the final bend, causing him to abort his lap and dart into the pits with a fluid leak. He sat out the remainder of the session.

Valtteri Bottas was fifth fastest in the second Mercedes, ahead of Renault’s Carlos Sainz, Haas’ Romain Grosjean, McLaren’s Fernando Alonso and Vettel down in ninth place after completing just 12 laps.

RED BULL JOY

In the first session of the day, Red Bull enjoyed a welcome return to the top of the timesheets after a few quiet races with Ricciardo and Verstappen securing a one-two for the team in the baking afternoon heat.

The demanding 23-turn circuit has traditionally favored the Red Bulls and Ferraris, so it was no surprise to see Vettel and Raikkonen clock the next quickest times as Mercedes opted to concentrate on long runs instead of qualifying simulations.

Ricciardo has failed to finish the last two grands prix since Formula One returned from its summer break but the Australian again showed his street circuit prowess by clocking one minute, 39.711 seconds in the scorching Singapore sun.

Dutchman Verstappen lapped in 1:39.912 to edge out Vettel by 0.085 seconds but the German will be looking for an improved third practice session and qualification on Saturday as he seeks to rein in Hamilton with seven rounds remaining.

“We can recover most of it tomorrow so we are not that worried,” Vettel told Sky Sports. “It looks like being close but we won’t really know until Sunday.”

Sauber’s Charles Leclerc continued to show the sort of form that encouraged Ferrari to sign him as Raikkonen’s replacement for next season by finishing ninth in an opening session that ended on a sour note when he crashed into a wall at Turn 13.

The 20-year-old apologized to his team on the radio as he left his car stranded in an escape road with two minutes left in the session, a sight that will disappoint his future employers, who will hope he does not make similar mistakes next season.