Seven of 10 Formula One teams returned to the pits after the warm-up lap, reducing the United States Grand Prix to six instead of 20 cars after their tyre partners Michelin voiced safety concerns, dpa reported. Renault with world championship leader Fernando Alonso, McLaren- Mercedes, BMW-Williams, Sauber-Petronas, Red Bull Racing, BAR Honda and Toyota with pole position holder Jarno Trulli did not compete after a last-ditch rescue plan in the form of a chicane to slow the cars down did not materialise, dpa reported. The Ferraris of world champion Michael Schumacher and Rubens Barrichello, the Minardis of Patrick Friesacher and Christijan Albers and the Jordans of Tiago Monteiro and Narain Karthikeyan - all with Bridgestone tyres - were left to fight out victory in the ninth season race. Michelin said they could not guarantee safety with the tyres they must use after failing to determine why their tyres failed on Friday which led to crashes of Ralf Schumacher and Ricardo Zonta. --SP 2235 Local Time 1935 GMT