Vettel highlights importance of Friday running at "tricky circuit" COTA

Ahead of this weekend's United States Grand Prix, Ferrari star Sebastian Vettel has underlined the importance of the practice sessions at the Circuit of the Americas as the German needs to understand where the tyre window is.

Vettel has finished three of the last four races in the top two places, getting P2 in Mexico behind rival Lewis Hamilton as Ferrari again failed to convert a front-row lock-out into a win.

The team will take comfort in the fact they won in Austin last season, however, with Kimi Raikkonen getting his first win in over 110 entries as the Finn broke the record for longest distance between two wins.

Vettel himself has only won once at the Circuit of the Americas in 2013, with Hamilton winning five of the seven races held in Austin at the purpose-built F1 circuit.

Looking ahead to this weekend, the four-time champion explained how much of a challenge 'COTA' is for drivers.

"The Circuit of the Americas is an exciting track, with a wide range of cornering speeds and lots of changes of direction," the 32-year-old said.

"It's quite bumpy, particularly in the big braking zones so it's easy to lock wheels there. The strategy choice is quite open, with both one and two-stop plans looking possible.

"It's a tricky circuit to get the tyres into the right performance window, so Friday running is important to understand the tyres and get prepared for the race."

Last year, as has happened before, Friday's running was very limited due to extreme rain, but this won't be the case this year.

"Last year's event was difficult because none of us got much useful running due to the poor weather on Friday. The forecast for this year is dry but quite cool. It should be a good circuit for us but, as we saw last year, we can take nothing for granted and the competition is also strong."