Fernando Alonso has warned that overtaking will be difficult on Sunday due to the new track surface in Miami.

The Spaniard's warning comes just days after many, including Mercedes team boss, Toto Wolff were critical of the Azerbaijan Grand Prix due to the lack of overtaking and the build-up of DRS trains.

Here, the problem isn't so much the shortened DRS zones - though this will no doubt add to the frustration come race day - but the condition of the newly asphalted Miami track which has received widespread criticism from drivers as they struggled for grip.

"It was a relatively routine Friday practice for us after the different format in Baku," said the Spaniard. "We've had more time on track to learn about the car and the tyres this weekend, despite some red flags disrupting the sessions.

"So far I think the new track surface seems to be better," he continued, "but we were basically just cleaning the racing line today. When you move away from it, it's very slippery so that could make overtaking difficult.

"Qualifying tomorrow is important, but our strength is normally on Sunday, so we'll see what we can do."

Indeed, the two-time world champion appeared to get a glimpse of what could happen on Sunday when he encountered traffic in the shape of the Alpine of Esteban Ocon, his former teammate.

Refusing to yield to the Aston Martin, Alonso told his engineer: "The Alpines are fighting the free practice!"

"That's a joke," replied his race engineer! "You were on a flying lap and Ocon didn't get out of the way."

"Copy," said the Spaniard. "But the free practice is their moment, so it's good."

"Obviously, it's new tarmac, it's a street circuit, it's dirty," said Nico Hulkenberg who crashed in the opening session. "The first run of P1 didn't feel great but I think we've seen a lot of track evolution as the day went on and certainly by the end of P2 things were much better."

Baku winner, Sergio Perez described the track conditions as feeling like he was driving on Intermediate tyres.

"The conditions out there are very low grip, especially in FP1," said the Mexican. "It felt like Inter conditions pretty much. We were measuring wet conditions to Inter conditions."

"Overall it's very tricky because there is only one line and whenever you get off-line there is really, really, poor grip," said Charles Leclerc, who crashed out of the second session.

"That's basically what happened," he continued, "I pushed too much, lost the rear, tried to recover from it but I had no grip to turn the car so that was it.

"No big damage," he added, "obviously the front right is gone but apart from that no damage to the rear of the car which is the most important but tomorrow is another day and I'm sure it will go well."

Check out our Friday gallery from Miami here.