Button Fastest in Practice 4 - Imola

Button, who qualified on pole position here last year, has suffered a disastrous season so far and is yet to finish a race after being blighted by reliability problems as well as a lack of pace.

But improvements in testing look to have improved the car significantly and his time of 1:20.058, the fastest of the weekend so far, put him 0.056 seconds clear of World Championship leader Fernando Alonso.

The order of the final practice, however, proved extremely tight, with the top ten drivers all covered by less than half a second.

Renault driver Alonso finished second, just ahead of third-placed driver Kimi Raikkonen's McLaren as Michael Schumacher finished fourth just 0.260 seconds off the pace.

Italian Giancarlo Fisichella finished fifth in the second Renault while Alex Wurz, replacing the injured Colombian Juan Pablo Montoya this weekend, was sixth fastest, just ahead of lead Williams driver Mark Webber, of Australia.

Webber's German teammate Nick Heidfeld finished eighth with Takuma Sato, of Japan, ninth in the second BAR-Honda and Felipe Massa, of Sauber, completing the top ten runners.

Michael Schumacher immediately bettered his previous best time of the day to put himself at the top of the timesheets and Raikkoen slotted into second place more than half a second down.

Portuguese driver Tiago Montiero spun in his Jordan into the gravel trap and stopped 15 minutes into the 45-minute session, limiting his running ahead of the qualifying session.

Raikkonen and then Button jumped ahead of Schumacher at the top of the timesheets as the session continued and the lap time moved closer and closer to dropping into the 1:19s.

Barrichello ran through a gravel trap with five minutes of the session remaining and finished down in 12th place and both PS05 Minardi cars stayed in the garage for the entire session.

Pos  Driver        Team                  Time                  Laps
 1.  Button        BAR-Honda         (M)  1:20.058               16
 2.  Alonso        Renault           (M)  1:20.114  +    0.056    8
 3.  Raikkonen     McLaren-Mercedes  (M)  1:20.209  +    0.151   10
 4.  M.Schumacher  Ferrari           (B)  1:20.318  +    0.260   13
 5.  Fisichella    Renault           (M)  1:20.351  +    0.293   18
 6.  Wurz          McLaren-Mercedes  (M)  1:20.358  +    0.300   11
 7.  Webber        Williams-BMW      (M)  1:20.424  +    0.366    6
 8.  Heidfeld      Williams-BMW      (M)  1:20.431  +    0.373    6
 9.  Sato          BAR-Honda         (M)  1:20.450  +    0.392   17
10.  Massa         Sauber-Petronas   (M)  1:20.506  +    0.448   11
11.  R.Schumacher  Toyota            (M)  1:20.802  +    0.744   11
12.  Barrichello   Ferrari           (B)  1:20.851  +    0.793   12
13.  Trulli        Toyota            (M)  1:21.105  +    1.047   14
14.  Coulthard     Red Bull-Cosworth (M)  1:21.136  +    1.078   12
15.  Villeneuve    Sauber-Petronas   (M)  1:21.543  +    1.485   11
16.  Liuzzi        Red Bull-Cosworth (M)  1:22.188  +    2.130   13
17.  Karthikeyan   Jordan-Toyota     (B)  1:22.964  +    2.906    8
18.  Monteiro      Jordan-Toyota     (B)  1:24.910  +    4.852    5
19.  Friesacher    Minardi-Cosworth  (B)  No Time                  
20.  Albers        Minardi-Cosworth  (B)  No Time                  

All timing unofficial