Oscar Piastri after co-leadership at McLaren with Lando Norris in Las Vegas

Norris is the main challenger to Red Bull's Max Verstappen, who will be sure of a fourth successive title this weekend if he beats the Briton.

Piastri has of late played a supporting role in the championship but the focus is now more on the constructors' championship, with McLaren leading Ferrari by 36 points and three rounds remaining.

"There’s still some, let's say, very specific scenarios where I might be needed to help out. But for the very large majority of situations, it's back to how it was," Piastri told reporters in Las Vegas.

"The drivers’ championship picture is very slim, and the constructors’ championship is certainly not over for us," he added.

"So it's a very specific few scenarios that maybe I'll still help out if that's what I'm asked to do, but I'm going into the weekend trying to win."

Piastri has two wins under his belt already this season, in Hungary and Azerbaijan.

Norris told reporters separately that the team had always come first and that would not change.

"Everything we've done, we've just swapped a position," he said.

"It benefited me because I was in the fight for the championship and that's the game we also have to play, just as I've helped Oscar in a few occasions and helped him win in Baku, you know. I did my job there.

"I think (team boss) Andrea (Stella) made it very clear from the beginning that we would never do something that would make the team result worse. So no, nothing is going to change."