Sochi, Russia - 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 suffered reliability problems.
Rosberg, chasing his seventh consecutive win 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 1m37.583s 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.
Also read: Hamilton needs a Russian hat-trick
The four-times world champion, whose team has 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.
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 it fights its 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. - Reuters
RESULTS
1 Lewis Hamilton (Britain) Mercedes - 1m37.583s
2 Sebastian Vettel (Germany) Ferrari - 1:38.235
3 Nico Rosberg (Germany) Mercedes - 1:38.450
4 Kimi Raikkonen (Finland) Ferrari - 1:38.793
5 Daniel Ricciardo (Australia) Red Bull - 1:39.084
6 Valtteri Bottas (Finland) Williams - 1:39.185
7 Daniil Kvyat (Russia) Red Bull - 1:39.193
8 Jenson Button (Britain) McLaren 1:39.196
9 Felipe Massa (Brazil) Williams - 1:39.289
10 Fernando Alonso (Spain) McLaren - 1:39.400
11 Carlos Sainz Jr (Spain) Toro Rosso - 1:39.465
12 Max Verstappen (Netherlands) Toro Rosso - 1:39.501
13 Nico Hulkenberg (Germany) Force India - 1:39.795
14 Sergio Perez (Mexico) Force India - 1:39.867
15 Kevin Magnussen (Denmark) Renault - 1:40.193
16 Romain Grosjean (France) Haas - 1:40.260
17 Esteban Gutierrez (Mexico) Haas - 1:40.508
18 Jolyon Palmer (Britain) Renault - 1:40.688
19 Felipe Nasr (Brazil) Sauber - 1:40.740
20 Rio Haryanto (Indonesia) Manor - 1:41.080
21 Pascal Wehrlein (Germany) Manor - 1:41.148