By Alan Baldwin
SOCHI, Russia (Reuters) - Formula One world champion Lewis Hamilton boosted his morale with the fastest lap in Russian Grand Prix practice on Friday after Mercedes team mate Nico Rosberg set the early pace and Ferrari (NYSE:RACE) suffered reliability problems.
Rosberg, chasing his seventh win in a row and fourth of the season, was quickest in the morning around the Olympic Park used for the 2014 Winter Games in the Black Sea resort.
The championship leader dropped to third in the afternoon, however, with Hamilton setting a best time of one minute 37.583 seconds on supersoft tyres compared to Rosberg's 1:38.450.
Ferrari's Sebastian Vettel stopped on track during the second session.
Hamilton is the only driver to have won in Russia since the race's debut in 2014 and he needs to complete the hat-trick on Sunday to eat into his team mate's hefty 36 point lead after just three of the 21 races.
The Mercedes pair, who have won 35 of the last 41 races between them, were comfortably ahead of the rest in the morning but Vettel was second fastest for Ferrari after lunch.
The four-times world champion, whose team have suffered power unit problems in two races this season, was halted by an electrical failure with an hour to go.
Ferrari's Kimi Raikkonen was fourth in both practices.
Australian Daniel Ricciardo, who tested a new head protection device at the start of the session and has finished fourth in all three races, was sixth and fifth for Red Bull in the two sessions. [nL3N17W2KX]
Russian team mate Daniil Kvyat was seventh, with McLaren's Jenson Button eighth and Fernando Alonso 10th in a boost for Honda-powered McLaren as they fight their way back up the pecking order after a nightmare 2015 season.
Renault's Russian test driver Sergey Sirotkin, who will be competing in the GP2 support series this season, replaced Denmark's Kevin Magnussen for the first session.
He ended up 13th fastest with regular race driver Jolyon Palmer 18th.