Lewis Hamilton led Nico Rosberg as Mercedes topped the P1 times in Bahrain
Alonso third fastest; Vettel P10 in opening session at Sakhir
By Mike Wise at Sakhir
Last Updated: 04/04/14 9:10pm
Hamilton, who is looking for his second victory in seven days in the Middle East this weekend, lapped the 5.412km Bahrain International Circuit in a time of 1:37.502s to go 0.231s faster than his team-mate.
Ferrari's Fernando Alonso was third fastest with Nico Hulkenberg (Force India), Jenson Button (McLaren), Kimi Raikkonen (Ferrari), Kevin Magnussen (McLaren), Daniil Kvyat (Toro Rosso) and Sergio Perez (Force India) next up.
World Champion Sebastian Vettel was tenth fastest with Red Bull team-mate Daniel Ricciardo 14th overall.
With this year's race taking place under floodlights, the 90-minute session was notable for a lack of running from some cars.
Held in bright, breezy - if not oppressively hot - conditions, it was clear they were considered unrepresentative by the likes of F1's current pacesetters.
Hamilton and Rosberg completed 14 and 13 laps respectively and appeared set to finish early with about half an hour to go. However, Alonso then nudged them down the order, with the W05s re-asserting themselves soon after.
With Alonso and Raikkonen both comfortable in the top ten, Ferrari look to have made a reasonable start to their weekend on a track where, although Mercedes are clear favourites, they'll hope to challenge Red Bull at least.
There was a comic moment earlier in the session, however, when Alonso left his garage only to notice that Ferrari's mechanics had placed a soft compound tyre on the left-front wheel of his F14 T by mistake.
The error was soon rectified, with the 0.4s gap to Hamilton doubtless giving Alonso and Ferrari heart as they head into the weekend.
Hulkenberg completed fewer laps, ten, than either Mercedes and while Vettel (16 laps) and Ricciardo (19 laps) managed a few more, the mileage racked up elsewhere - Lotus's Pastor Maldonado and Romain Grosjean respectively completed 31 and 24 - suggested where teams' priorities currently lie.
The lights will be on when P2 starts at 6pm local time (4pm BST).