Mercedes drivers Nico Rosberg and Michael Schumacher think that the United States Grand Prix will be tough due to the length of time the tyres take to warm up.
"The car felt better than at the last race. The conditions were tricky, particularly this morning, as it was very cold which meant that the tyres were really on the edge", said Rosberg.
Schumacher, taking part in his penultimate race, added "The track is still very green, especially offline, but it delivers lots of potential for a good show. As for our programme today, we had some tyre issues in the second session with a puncture which affected our plan a little. However, I will just try to do my best tomorrow and in the race on Sunday".