Trulli on top as rain reaches Indy.

Jarno Trulli played a waiting game during the first free practice session of the United States Grand Prix weekend, but even the canny Italian could not have predicted that he would come out on top of the times.

Having narrowly eased ahead of Renault team-mate Fernando Alonso during the two-hour Heathrow testing session that preceded practice, Trulli duly sat out the first half of the one-hour follow-up before putting all his hard-earned knowledge to the test and coming out with the fastest time of the session. The Italian was aided first by a red flag incident that allowed him a run on a relatively clear circuit, then, when the rest of the expected frontrunners were massing for a crack at his time, watched as the threatened rain clouds rolled in and soaked the track.

Chasing the Renault driver - who had headed extra testing by just 0.001secs over Alonso - was Ralf Schumacher, clearly healthier than he had been at Monza, and determined to show all and sundry that he was still able to run at the front after his Monza test shunt.

The German set the initial pace, having ventured out onto the Indianapolis road course as soon as the pit-lane opened, and then entered into a tug-of-war for fastest time with Alonso and brother Michael, who was keen to underline Ferrari's recent revival. Schumacher Jr returned to the head of the times shortly before the red flag flew, but was then usurped by Trulli within a lap or so of it being withdrawn. The rain subsequently put paid to any hope the German had of capping his comeback with top spot.

Third place went to another Michelin runner, Olivier Panis, the Frenchman apparently not harbouring any disruptive thoughts about his father's reported arrest. using the potent power of the Toyota V10, Panis managed to get between Schumacher and the leading Ferrari of Rubens Barrichello, heading the Brazilian by a tenth of a second.

After its dominating 1-3 result on home soil at Monza, Ferrari was keen to point out that its revival was not just due to Michelin having to revise its tyre supply, with all the disruption that would have caused to its customers' preparations for the final European round. Although the world champion did top the times midway through the session, however, he was gazumped not only by three Michelin runners, but also by team-mate Barrichello, who squeaked ahead shortly after the resumption.

Alonso took sixth place as Michelin showed its fighting qualities by annexing eight of the top ten positions, edging out Mark Webber's Jaguar which, like the Spaniard's Renault, had benefited from two extra hours running on the green circuit.

Juan Montoya was only eighth overall, but trailed championship rival Schumacher by a mere couple of tenths in a session he will probably regard as inconsequential. The Colombian also completed one of the lowest lap totals, three less than the German, with whom he circulated briefly during the wet finale.

The third title contender, Kimi Raikkonen was next up, 0.03secs slower than the Williams-BMW, having completed 26 laps, nine of which came in the wet as he prepared for the conditions likely to affect qualifying later this afternoon. McLaren-Mercedes team-mate David Coulthard rounded out the top ten.

Cristiano da Matta maintain the Michelin domination of practice by taking eleventh place on his Indianapolis debut - the Brazilian had not been there even during his CART days - and was the final runner within a second of the outright pace set by Trulli.

Jenson Button and Jacques Villeneuve continued to prove that BAR-Honda is the best of the rest in terms of the Bridgestone runners, sandwiching Justin Wilson in 13th spot as they completed the highest number of laps of any team, with 28 and 29 respectively. Wilson, meanwhile, used the session to build on his scanty knowledge of both the circuit and the Jaguar R4, winding up six-tenths shy of team-mate Webber.

Giancarlo Fisichella continued his mixed start to the weekend by taking an encouraging 15th spot, a couple of tenths short of matching Villeneuve, but also completing just eight laps as his expiring Ford engine brought out the red flag after coating the banked final corner in oil. The Italian had been hoping to build on his track time during the session, after only completing 17 laps in the two-hour Heathrow session following earlier technical gremlins.

Jordan team-mate Ralph Firman marked his return to action by chasing his team-mate throughout the session, eventually winding up three-tenths shy as he continued to learn another circuit new to him in 2003. The Briton, who was making his first real foray back into the cockpit following his Hungarian GP practice crash, completed 19 laps, but also saw his session end with a walk back to the pits.

He was followed by another circuit novice, Nicolas Kiesa, who continued to look ragged but gradually came to grips with his Minardi-Cosworth on the still largely gripless surface. His time was good enough to see off both Saubers, which singularly failed to come to terms with the circuit, leaving Nick Heidfeld and Heinz-Harald Frentzen to take 18th and 19th places, albeit some way ahead of the luckless Jos Verstappen.

The Dutchman had been sidelined late in the extra testing session as his Minardi ground to a halt, and managed to complete just 15 laps in free practice after starting late and running into more trouble. It was perhaps a mark of his problems that his fastest time of the session was set after the rain had set in....