I expect a tough Bahrain battle, insists Hamilton
Sebastian Vettel finished ahead of team-mate Charles Leclerc as Ferrari's bid to relaunch their Championship challenge began in perfect fashion in Bahrain.
The Italians were blown away by a dominant Mercedes team at the season-opening race in Melbourne a fortnight ago.
Vettel, however, ended second practice at the Sakhir circuit six tenths of a second clear of rival Lewis Hamilton, who was third.
Valtteri Bottas, leading the Championship after winning the first race, trailed in fourth.
Ferrari left Melbourne scratching their heads after their pre-season form deserted them.
Mercedes topped every practice session in Australia, before Hamilton secured pole and Bottas galloped to a convincing win.
Their mood will be rather better here, with the evidence suggesting it may not be a one-team race for the title.
"The Ferraris have been quick from the get-go and picked up more pace from there, so it's completely different to what we've seen in Melbourne," said world champion Hamilton.
"We had some issues with the balance of the car, but we made improvements for FP2. At the moment it looks like the Ferraris are ahead, so we have to keep our heads down, keep working, analyse things tonight and try and come back stronger tomorrow.
"As we get to qualifying, everything will get a little closer, but it is going to be tough."
Ferrari team principal Mattia Binotto supported that view, saying he thought the riday practice were "misleading" and that he believed Ferrari had been running their engines more aggressively than Mercedes.