Spain's Carlos Checa edged out Daijiro Kato to claim pole position in a rainy qualifying session for Sunday's Portuguese MotoGP.

Checa roared round the Estoril circuit in a time of one minute 39.793 seconds on his Yamaha, 0.075secs quicker than Kato's Honda.

Italy's runaway championship leader Valentino Rossi, winner of eight of the 10 races so far this season, was third fastest on his Honda with 1:39.984.

Despite persistent rain, all three beat Friday's fastest qualifying time set by Brazil's Alex Barros, who had to settle for fourth on the grid.

Porto on pole

Most riders only took to the track in the second half of the session due to the wet surface.

"We only had 20 minutes, it was like Formula One," said Checa, who last won a Grand Prix in 1998.

Sebastian Porto of Argentina took pole in the 250cc class, clocking 1:41.706secs on his Yamaha.

Italy's Marco Melandri was second with 1:42.097 on an Aprilia and Spain's Fonsi Nieto was third with 1:42.325.

Spain's Daniel Pedrosa was quickest in the 125cc class on a Gilera ahead of team-mate Manuel Poggiali of San Marino.

Pedrosa clocked a fastest lap of 1:46.664, beating Poggiali's quickest time from Friday's qualifying session.

Japan's Youichi Ui on a Derbi and Germany's Steve Jenkner on an Aprilia were tied for third with 1:47.113.

Saturday's Estoril qualifying times:

MotoGP
1 Carlos Checa (Spa) Yamaha, 1min 39.793secs
2 Daijiro Kato (Jap) Honda, 1:39.868
3 Valentino Rossi (Ita) Honda, 1:39.984
4 Alex Barros (Bra) Honda, 1:40.112
5 Max Biaggi (Ita) Yamaha 1:40.147
6 Jeremy McWilliams (GB) Proton KR3, 1:40.308
7 Loris Capirossi (Ita) Honda,1:40.315
8 Tohru Ukawa (Jap) Honda, 1:40.509
9 Sete Gibernau (Spa) Suzuki, 1:40.747
10 Jurgen Vd Goorber (Neth) Honda, 1:40.771

250cc
1 Sebastian Porto (Arg) Yamaha, 1min 41.706secs
2 Marco Melandri (Ita) Aprilia, 1:42.097
3 Fonsi Nieto (Spa) Aprilia,1:42.325
4 Roberto Rolfo (Ita) Honda, 1:42.353
5 Franco Battaini (Ita) Aprilia,1:42.430
6 Toni Elias (Spa) Aprilia, 1:42.451
7 Emilio Alzamora (Spa) Honda 1:42.591
8 Naoki Matsudo (Jap) Yamaha, 1:42.652
9 Randy De Puniet (Fra) Aprilia, 1:42.916
10 Alex Debon (Spa) Aprilia, 1:43.259

125cc
1 Daniel Pedrosa (Spa) Honda, 1:46.664
2 Manuel Poggiali (San Marino) Gilera, 1:46.872
3 Youichi Ui (Jap) Derbi, 1:47.113
4 Steve Jenkner (Ger) Aprilia, 1:47.113
5 Mika Kallio (Fin) Honda 1:47.320
6 Simone Sanna (Ita) Aprilia, 1:47.373
7 Mirko Giansanti (Ita) Honda,1:47.502
8 Lucio Cecchinello (Ita) Aprilia,1:510
9 Arnaud Vincent (Fra) Aprilia,1:47.562
10 Alex De Angelis (San Marino) Aprilia, 1:47.566