Drivers found more grip at the Circuit of the Americas on their second visit to the circuit but as in 2012 should only need to make one pit stop for tyres.
Heikki Kovalainen passed his first test as a Lotus driver with flying colours, ending the first day fifth fastest overall.
Pictures from the first day of practice for the United States Grand Prix.
F1 car designers believe unreliability will be a much bigger factor in 2014 and could decide the outcome of the championships.
Red Bull chief technical officer Adrian Newey has warned the 2014 regulations will force designers into creating unattractive cars.
Enter your United States Grand Prix predictions to win loads of F1 prizes this weekend.
Sebastian Vettel led a Red Bull one-two in the second practice session at the Circuit of the Americas.
Jenson Button has been given a three-place penalty for the United States Grand Prix.
Follow the 2013 United States Grand Prix second practice session on F1 Fanatic Live.
Fernando Alonso headed first practice at the Circuit of the Americas but the session was delayed twice due to poor visibility and problems with the medical helicopter.
Follow the 2013 United States Grand Prix first practice session on F1 Fanatic Live.
Sebastian Vettel topped of the driver of the weekend poll for the sixth time this season following his dominant drive to victory in Abu Dhabi.
In the round-up: Hulkenberg turned Lotus down ?σΤιΌ?σ Maldonado ‘delivered more to Williams than they did’ ?σΤιΌ?σ Magnussen a “massive risk” – Button