Kiwi driver Brendon Hartley's had his first taste of Formula 1 action in Saturday's (NZ time) opening practice session at the United States Grand Prix in Texas.

The 27-year old was 14th fastest, almost three seconds off the pace set by championship leader Lewis Hamilton, who had a time of 1m, 36.335s.

If Hamilton wins Monday's (NZ time) race and Sebastian Vettel finishes lower than sixth, the British driver will secure his fourth championship.

In another twist of events, during Hartley's practice session the Australian flag appeared next to his name on the driver's list, which will likely frustrate New Zealand motorsport fans as Hartley is the country's first Formula 1 driver since 1984.