Lewis Hamilton pipped Mercedes team-mate Nico Rosberg in the final practice session before qualifying at the Russian Grand Prix.
The British world champion, who trails the German by 36 points in the championship after three races, was just 0.068 seconds ahead of Rosberg.
Ferrari's Sebastian Vettel, who has a five-place grid penalty, was third, but 0.604secs adrift of the Mercedes.
Ferrari's Kimi Raikkonen was fourth, ahead of Williams' Felipe Massa.
Qualifying is live on the BBC Sport website and 5 live Sports Extra at 13:00 BST.
Hamilton is determined to win this race and narrow the gap Rosberg has built up with three straight wins and a difficult start to the season for the 31-year-old.
If anything, Rosberg was the more consistent of the two drivers during a fascinating session in which the low abrasiveness of the Sochi track enabled drivers to keep pushing hard on the tyres for several laps, an unusual phenomenon with these high-degradation Pirelli tyres.
Hamilton had a number of runs in which he was quickest of all in one or two sectors, but made errors in another.
But he saved the best for last, jumping to the top of the timesheet with his final fastest lap.
Mercedes appear comfortably clear of Ferrari - and their biggest threat for a win, if they have one, has effectively been removed with Vettel's penalty.
Williams, who have had a difficult start to the season, have had an encouraging weekend so far, with Massa's team-mate Valtteri Bottas in sixth ahead of the Toro Rosso of Max Verstappen.
Jenson Button - who is very strong on the Sochi street track - raised McLaren hopes of getting into the final qualifying session for the first time in their new Honda era with the eighth fastest time, four places and 0.4secs ahead of his two-time champion team-mate Fernando Alonso.
The two McLarens were separated by the second Toro Rosso of Carlos Sainz, Force India's Sergio Perez, who had a spin at Turn 13 early in the session, and Red Bull's Daniel Ricciardo, who did his fastest lap out of sequence earlier in the session.