Formula 1 championship leader Kimi Antonelli reckons Mercedes has made another step trying to extract performance from its recent upgrade package at the United States Grand Prix.

Mercedes arrived at Austin's challenging Circuit of the Americas with a new front wing option to further complement its significant upgrade package introduced in Malaysia two races ago. That initial upgrade raised the performance ceiling of the car, but also made it more peaky and harder to optimise.

With both Antonelli and George Russell now on the latest specification after splitting packages in Singapore, Mercedes' progress from first to second practice in Austin suggested the W17 is still difficult to get in the right operating window.

But when the magic happens there is performance to be found, with Antonelli just 0.042s behind Ferrari's FP2 leader Charles Leclerc on Friday.

"I felt better in the car compared to FP1," Antonelli said. "There is still lots of work to do, but it was a good step forward and now we'll try to improve even further. Having both cars on the same package helps, because we can try lots of different stuff and we can have a better understanding of this package.

"Since Singapore we were able to analyse the data and understand better what this package needs. We're still trying to find how to put the car in the right window, but we've been taking steps forward and we'll see what we can do to improve even more."

Kimi Antonelli, Mercedes

Photo by: Simon Galloway / LAT Images via Getty Images

Initial reads from the long runs suggested all four top teams are fairly evenly matched, with perhaps Red Bull and Ferrari slightly ahead of Mercedes and McLaren, setting up an intriguing weekend in Texas.

Trackside engineering director Andrew Shovlin added: "We didn’t have a good first session. We were looking to explore a wider set-up window with the update package on both cars, but we were struggling with locking, which was a big limitation in both our single-lap work and the long runs.

"We repositioned the cars going into the afternoon session and that seems to have put us in a better place. We had fewer balance issues, the car was more predictable, and the lap times improved as a result."

Russell only managed fifth, seven tenths behind Leclerc, after not getting a proper lap in - his first soft tyre effort scratched for exceeding track limits and his second ruined by a huge snap through the fastest portion of COTA's Esses.

The story of Saturday qualifying will not just be about ultimate car performance, but also about keeping Pirelli's soft tyres alive through the demanding final sector, with several drivers locking up or going off the track as the rear rubber started fading in qualifying simulations.

"I think it's just all about keeping the rear tyres in good shape through that twisty bit so that you've got the performance in the last corner," said deputy team principal Bradley Lord.

Bradley Lord, Deputy Team Principal, Mercedes AMG F1 Team

Photo by: Andy Hone/ LAT Images via Getty Images

"It's just getting the set-up in the right place and getting the car able to rotate without needing to overuse the rear tyres, overuse the throttle and if we can do that then we should be in good shape."

Austin is theoretically the first opportunity for Antonelli to seal his maiden world championship. But as that would involve the Italian winning the race with Russell finishing ninth or lower - and Lewis Hamilton finishing fifth or lower - it's not a scenario Mercedes is overly preoccupied with.

"Ultimately, for Kimi to win this weekend it means the team's had a really bad race, because the maths say George needs to be ninth or below, and that isn't how we want to go racing and the result we're aiming for," Lord pointed out.

"So, it's a very minimal chance, it's theoretically possible, but in practical terms, this isn't the match point weekend. We'll just try and get out there, get as many points as possible and then see when the maths start to come towards us a little bit more."