Vermeulen takes pole at wet Assen

The track was wet throughout Dutch Grand Prix qualifying, but dried very slightly in the middle of the session, before heavier rain fell with a quarter of an hour remaining.

Just as the downpour resumed, Vermeulen completed a 1:48.555 lap and knocked championship leader Casey Stoner off pole by 0.017 seconds.

It looked like the grid was then set as the rain continued to come down, but several riders stayed out and managed to make big improvements in the final seconds.

Randy de Puniet leapt from 13th to third with the final lap of the session, while Marco Melandri moved from the midfield to fourth - giving Gresini Honda a boost after Toni Elias leg-breaking practice crash.

But Rossi was unable to make similar progress. He had struggled with his settings early on and did not get a good lap in before the rain returned. He was down in 15th at this stage and rejoined on his spare bike with a different set-up. But although Rossi found more speed, he could not replicate de Puniet and Melandri's efforts and will start 11th.

Stoner had dominated the early part of qualifying, holding provisional pole by up to three seconds as others found their feet on the wet track.

Dani Pedrosa briefly usurped Stoner after 20 minutes, but the Australian was soon back in front, and stayed there until Vermeulen's perfectly-timed lap.

John Hopkins completed the top five on the second Suzuki, with Colin Edwards sixth ahead of Kawasaki's Anthony West.

The Australian newcomer had been second only to Stoner in the first part of the session, but was in the pits when conditions were at their best and fell down the order. He rejoined in the final minutes and managed to get back up to seventh.

Alex Hofmann continued Pramac D'Antin's promising weekend in ninth, with Loris Capirossi taking 10th.

Although he had shown much better form in dry practice, world champion Nicky Hayden also struggled for speed in wet qualifying and will start 13th.

Pos  Rider             Bike      Time
 1.  Chris Vermeulen   Suzuki    1:48.555
 2.  Casey Stoner      Ducati    1:48.572  + 0.017
 3.  Randy de Puniet   Kawasaki  1:49.579  + 1.024
 4.  Marco Melandri    Honda     1:49.679  + 1.124
 5.  John Hopkins      Suzuki    1:49.684  + 1.129
 6.  Colin Edwards     Yamaha    1:49.691  + 1.136
 7.  Anthony West      Kawasaki  1:49.807  + 1.252
 8.  Alex Hofmann      Ducati    1:49.927  + 1.372
 9.  Daniel Pedrosa    Honda     1:50.132  + 1.577
10.  Loris Capirossi   Ducati    1:50.169  + 1.614
11.  Valentino Rossi   Yamaha    1:50.392  + 1.837
12.  Alex Barros       Ducati    1:50.402  + 1.847
13.  Nicky Hayden      Honda     1:50.581  + 2.026
14.  Kurtis Roberts    KR        1:51.259  + 2.704
15.  Shinya Nakano     Honda     1:51.827  + 3.272
16.  Carlos Checa      Honda     1:53.271  + 4.716
17.  Sylvain Guintoli  Yamaha    1:54.253  + 5.698
18.  Makoto Tamada     Yamaha    1:57.525  + 8.970