SOCHI, Russia - Ferrari have a significant speed advantage down the Sochi straight and appear to have the 'perfect package', Mercedes Formula One boss Toto Wolff said on Saturday after his team were outqualified in Russia for the fourth race in a row.

Ferrari's pole sitter Charles Leclerc lapped 0.4 seconds faster than Mercedes's five-times world champion Lewis Hamilton, albeit on a different tyre strategy.

It was Leclerc's fourth pole in a row, making the 21-year-old Monegasque the first Ferrari driver to do that since Michael Schumacher in 2000 -- the start of a golden and dominant era for the Italian team.

"We are losing seven to eight tenths on the straight, and that's quite a massive amount," Wolff told Sky Sports television.

Ferrari won at flat-out high-speed circuits Spa-Francorchamps and Monza but also at tight and twisty Singapore. Sochi is different again and the Italians are looking good there as well.

"It seems to be like the perfect package," said Wolff of a car that has bags of power on the straight but also the aerodynamic downforce to retain the advantage through the corners.

Mercedes have yet to be beaten in Sochi since the race appeared on the calendar in 2014 but Sunday has been held up as a real benchmark of Ferrari's resurgence.

"They go to another level. You know that whole 'party mode' you talked about us having They have something else beyond that -- jet mode," said Hamilton, who qualified in second place.

The Briton, 65 points clear of Mercedes team mate Valtteri Bottas with six races to go, opted for the medium tyres with Leclerc on softs.

"We know they (Ferrari) are on a slightly lower drag level this weekend, plus they have that power, so we've got to try something," said Hamilton.

"I think the team have done a really good job with putting us in that position."

A one-stop strategy has traditionally been quickest in Russia but the jury is out on whether it is best to start on softs or medium, and for how long to run, before going to harder rubber.

Hamilton said Sochi, with its smooth surface and long drag to turn one, was not always the best for starting on the harder compound but he would do his best to get a tow from Leclerc if the chance arose.

(Wriitng by Alan Baldwin in London, editing by Clare Fallon) ((alan.baldwin@thomsonreuters.com; +44 2075427933; Reuters Messaging: Reuters Messaging: alan.baldwin.reuters.com@thomsonreuters.net))