Ferrari quickest in shortened first session.

Rubens Barrichello headed a Ferrari 1-2 ahead of world champion Michael Schumacher in the truncated opening free practice session for the Belgian Grand Prix at Spa-Francorchamps.

Run over half an hour because of a delay caused by early morning fog over the Ardennes, the session prompted most participants to head out early but, as usual, Ferrari was the last to emerge from the pit-lane, with neither driver venturing out until almost a third of the session had elapsed. It mattered little, however, as Barrichello and Schumacher entertained themselves in a private duel for top spot - heading the rest of the field by over a second.

The German obliterated his team-mate's opening salvo, having felt that he could have set the pace on an earlier lap only to be held up by Spa nemesis David Coulthard. Barrichello, however, retaliated in the closing two minutes by eclipsing the champion's best lap by 0.025secs.

Coulthard was the only driver to get remotely close to the scarlet cars, but still had to settle for being over a second adrift as the flag fell. Ironically, it was McLaren team-mate Kimi Raikkonen who had the honour of posting a fastest time during the session, with DC putting in his best laps when the Ferraris had already moved to the front. Raikkonen, however, ended the session on a low note, his car twitching violently approaching Blanchimont and forcing the young Finn to use the old pit-lane entrance in his concern to return the car to the pit area.

Jarno Trulli, one of the drivers to speak out in favour of the 'Eau Rouge challenge' in the week leading up to the event, split the two McLarens in fourth spot, but lapping some 1.8secs off Barrichello's pace. Renault team-mate Jenson Button posted the eighth best lap of the session to back the Italian up.

Sixth went, surprisingly, to Eddie Irvine, the Irishman trying out Jaguar's revised front suspension for the first time and putting it to good use by mixing with the likes of Renault and Jordan in the lower half of the top ten. Team-mate Pedro de la Rosa was slightly further back, in 14th place, eight-tenths off Irvine.

Seventh fell to Takuma Sato, the Japanese hotshoe clearly revelling in a circuit he knows and allows him to demonstrate both his bravery and car control. As high as fifth mid-session, the Jordan driver slipped back as Trulli and Irvine found time late on, but still managed to out-pace last year's podium finisher, Jordan team-mate Giancarlo Fisichella, to the tune of almost half a second.

Mika Salo, shortly to retire, and Ralf Schumacher rounded out the top ten, with the former's Toyota team-mate taking eleventh in a relatively good session for Michelin. There was less fortune for Schumacher's Williams team-mate Juan Montoya, however, the Colombian suffering a gearbox problem that restricted him to just three laps and last place on the timesheets.

Neither Sauber not BAR sparkled as they had in the altogether different opening session in Hungary, with Nick Heidfeld lead the way in twelfth place. The German squeaked ahead of Fisichella, but team-mate Felipe Massa was only 17th as he rediscovered a track he last visited in Formula Renault. Jacques Villeneuve had the upper hand in the BAR camp after both he and team-mate Olivier Panis set the early pace, but was restricted to 15th overall. Panis, meanwhile, grenaded a Honda engine in the closing minutes and, with just half an hour scheduled until the second session, may find his work done for the day.

Over at Minardi, Anthony Davidson held a 0.002secs advantage over Mark Webber, with both drivers comfortably inside the 107 per cent time despite the Englishman finding himself without traction control at La Source on one lap.