Red Bull driver Mark Webber set the fastest time in Friday's practice for the Formula One Japanese Grand Prix, edging McLaren driver Lewis Hamilton and teammate Sebastian Vettel.
Webber was ahead of the Mercedes-bound Hamilton by 0.214 seconds in the afternoon practice at the Suzuka circuit. Vettel was third, a further one-tenth back.
"The car ran well and we tested both tires,'' Webber said.
"We have areas where we can improve, mostly with the balance, so we have some work to do.''
Hamilton, who won the Japanese GP in 2007 when the event was staged at Fuji Speedway but has never taken top honours at the Suzuka circuit, said he expects a tough challenge from the Red Bulls on the weekend.
"It looks very close between ourselves and Red Bull,'' he said.
Michael Schumacher - who announced on Thursday that he will retire at season's end - was 10th in practice. The Mercedes driver spun off the track at the Spoon Curve, slamming into a bank of tires. He walked away from the incident and appeared unhurt.
Force India driver Paul di Resta also lost control of his car at the same curve and was unable to continue.
Force India's Nico Hulkenberg was forth, ahead of championship leader Fernando Alonso of Ferrari. Lotus' Romain Grosjean was sixth and moved in front of 2011 Japanese GP winner Jenson Button, who led much of the afternoon session but couldn't stay ahead.
Williams driver Bruno Senna and Ferrari's Felipe Massa were eighth and ninth respectively.
Lotus' Kimi Raikkonen, who is third in the standings and maintains title hopes despite not having won a race in his comeback season, had a KERS problem and finished 14th.
Vettel trails Alonso by 29 points in the standings and is aiming to make up more ground in Sunday's 53-lap race. The German driver won the previous race in Singapore and has traditionally done well in Japan - winning here in 2009 and 2010.
Alonso hasn't won since the German GP in July and his series lead has been cut with six races to go.
Webber has won twice this year - at Monaco and Silverstone - and is fifth in the standings.