The Fort Worth Press - Leclerc on top for Ferrari ahead of Verstappen and Piastri

The Monegasque driver clocked a best time in one minute and 29.310 seconds to outpace his Dutch rival by 0.164 seconds and finish four-tenths clear of Piastri as championship leaders Mercedes were pushed aside.

Seven-time champion Lewis Hamilton was fourth in the second Ferrari ahead of Italian teenager Kimi Antonelli of Mercedes, the youngest leader of the title race in F1 history, with George Russell sixth in the second Mercedes.

World champion Lando Norris was seventh in the second McLaren ahead of Alpine's Pierre Gasly, Isack Hadjar in the second Red Bull and Carlos Sainz of Williams as the teams with most upgrades appeared to gain from their improvements.

Mercedes, with no significant changes to the cars that had won the first three races before the cancellations of events in Bahrain and Saudi Arabia, were unable to exert their usual authority.

After a five-week hiatus due to the conflict in the Middle East, Sainz was the first man out ahead of the two Ferraris, all of them seeking early feedback on their extensive upgrades on a warm morning in the Sunshine State.

- Engine rules issues -

It had emerged overnight that F1's engine rules for 2027 were expected to be decided within two weeks and ahead of the Canadian Grand Prix, introducing speculation about a move away from 50/50 to a 60/40 split between engine and electrical power.

This was an issue sure to provoke more discussion and perhaps decide the futures of some drivers, including four-time champion Max Verstappen and two-time champion Fernando Alonso.

Verstappen has criticised the new hybrid era cars for producing artificial racing and said he was considering ending his F1 career.

Alonso, at 44, had also said he was ready to decide on his future with struggling Aston Martin.

Hamilton said he welcomed the recent dialogue between drivers and ruling bodies, but wanted to see the drivers offered a permanent voice when future rule changes are discussed.

"The drivers all work together," he said. "We meet and talk, but we don't have a seat at the table, which I think needs to change."

On track, Norris soon showed McLaren's speed to take control while Russell complained his car's turbo sounded like a steam train and Gasly reported a curious smell from his Alpine.

After 46 minutes, Leclerc grabbed the initiative in 1:29.885 ahead of Antonelli with Hamilton, also in a Ferrari, going third.

It appeared that the heavily revised Ferrari, sporting 11 new parts, was responding well to the team's investment –- the most of any team, ahead of McLaren, while Aston Martin had none and Haas just one.

After an hour of the only practice session, extended to allow more time for preparation with the new cars at a sprint race weekend, both Verstappen and Hadjar were complaining of gearbox problems.

"The shifts are horrendous, up and down," said the Dutchman.

With 15 minutes remaining, the top contenders pitted for soft-tyre runs and an opportunity to prepare for sprint qualifying later in the day.

Antonelli, who took sprint pole last year, was unable to run due to a power-unit issue as Leclerc stayed top ahead of Verstappen, Piastri and Hamilton.

A.Williams--TFWP