Nico Rosberg has warned the friendly relationship between Carlos Sainz and Lando Norris won't last as McLaren improve.

The two drivers have built a strong rapport in their first season together at the British team and a continuation of their partnership has already been confirmed for 2020.

However, with McLaren strong favourites to finish fourth in the Constructors' standings this season and harbouring ambitions of joining the top three teams from 2021, the former world champion believes that, as the stakes grow higher, tensions will creep in.

"They are racing for 10th place. If they were racing for a world championship it would change rapidly, mark my words," he said via F1i.com.

"You can’t be friends. You can only be friends if there is a clear number one and two. If you have got two guys who are trying to beat each other, it is impossible to be friends.

"You are so ego-driven and within a team, the politics going on are so big," he suggested.

"You are fighting for a world championship and there’s so much at stake that unfortunately, that becomes more important than friendship."

It was this view which the German took when fighting Lewis Hamilton at Mercedes, as a more selfish approach earned him a Formula 1 title at the third attempt in 2016.

Rosberg also believes it is an approach that Valtteri Bottas needs to adopt if he has any chance of taking on the five-time champion.

Also Read:

• Sainz only interested in working with Norris to push McLaren forward
• McLaren wanted to stop teams 'sniffing around' by confirming 2020 line-up

At McLaren, however, Norris believes a lot of teammate relationships are different to what fans and pundits see publicly.

"I guess you see a lot of stuff on TV where teammates are laughing with each other and everything, but as soon as they go behind closed doors they, like, hate each other," he told Reuters.

"That’s all fake, but I think we’re just good friends. We get along, we have fun.

"I don’t know if it’s something he’s always had, but it’s definitely something I’ve always had with my teammates 99% of the time."