Reigning MotoGP champion Casey Stoner set the fastest lap time during morning warm-up for the US MotoGP at Laguna Seca, which saw pole sitter and title leader Jorge Lorenzo one of three riders to fall.

The session had been delayed by an hour due to morning fog and conditions were still cold (air 13 degrees) and moist when the 20-minute session eventually got underway.

Double home winner Nicky Hayden began the day with a bang when he ran straight on and slammed into an airfence on his out-lap.

The newly re-signed Ducati rider clung on throughout, only toppling off due to the force of the rebound from the air fence. Hayden got the bike back to the pits and seemed to indicate brake problems to his crew.

Alvaro Bautista was next to fall, losing the front into the final turn just before the halfway stage, with Lorenzo suffering the same fate at the same turn shortly after.

The Yamaha star sprinted over to his bike to turn off the engine, having already lost one of his six due to the Assen accident caused by Bautista.

Lorenzo then ran back to the pits for his spare bike and returned to top the session, before second-place starter Stoner went 0.001s faster just before the chequered flag was waved.

Stoner's best lap was just under one-second from Lorenzo's pole time.

All the signs are that victory will be a Lorenzo/Stoner/Dani Pedrosa battle, with Pedrosa also leading this morning's warm-up on his way to third and just 0.147s from Stoner.

Pedrosa, using the new RCV, will start from the outside of the front row and 19-points from Lorenzo.

Andrea Dovizioso got the better of Yamaha Tech 3 team-mate Cal Crutchlow to be the top satellite rider this morning. The Italian was 0.496s from Stoner, with Crutchlow 0.666s adrift.

Ben Spies, who injured his heel in a qualifying highside, was passed fit to ride this morning and was the final rider within one-second of Stoner, in sixth.

The Texan will start his final US Grand Prix for Yamaha from fourth on the grid.

Stefan Bradl was seventh for Honda LCR, with Hayden recovering from his earlier set-back to be the lead Ducati in eighth place (1.294s). Team-mate Valentino Rossi, who has qualified just tenth, was a fraction slower for ninth.

Top CRT rider Randy de Puniet (Aspar) took tenth place (+2.436s) but CRT wild-card Steve Rapp (Attack Performance) lost his final last chance to qualify for the race when he failed to set a lap time.

Rapp was outside the 107% pole time limit by 0.695s on Saturday but the rules now allow a further chance in warm-up.

Despite the warm-up delay, the race will start as planned at 14:00.

Warm-up:

1. Casey Stoner
2. Jorge Lorenzo
3. Dani Pedrosa
4. Andrea Dovizioso
5. Cal Crutchlow
6. Ben Spies
7. Stefan Bradl
8. Nicky Hayden
9. Valentino Rossi
10. Randy De Puniet
11. Aleix Espargaro
12. Karel Abraham
13. Yonny Hernandez
14. Alvaro Bautista
15. Toni Elias
16. James Ellison
17. Ivan Silva
18. Michele Pirro
19. Colin Edwards
20. Danilo Petrucci
21. Mattia Pasini
Steve Rapp