London: Lewis Hamilton is enjoying the intensity of his Formula One rivalry with Ferrari's Sebastian Vettel, even if the Mercedes driver recognises that the smiles could suddenly turn sour.

The two men, with seven world championships between them, fought a wheel-to-wheel duel in Spain on Sunday with Hamilton emerging the winner and now six points behind the German.

Each has two wins this year from five races. "What I love about the race with Sebastian is this... I love tennis, I love watching (Roger) Federer and (Novak) Djokovic in a final, and what I really admire is the consistency... Every hit of that ball, just one misplaced or (in) the net can mean the whole game. So I admire their concentration and how they are so awesome and stay at the limit. I felt today I had that battle with Sebastian," Hamilton said.

Hamilton, a triple champion, has had a dominant car and his teammate as main rival for the past three years, but Nico Rosberg's abrupt retirement after winning the 2016 title has changed that.

He is now up against a quadruple champion, once dominant with Red Bull, who has a machine to match the Mercedes. Racing against a teammate - with the constructors' championship always a consideration and the same strategist calling the shots for both - can never be as no-holds barred.

Last year in Spain, the Mercedes drivers collided at the start - leaving Hamilton 43 points adrift of Rosberg.

"Having a battle and a fight with another team, it's so much more enjoyable," said Hamilton, whose new teammate Valtteri Bottas won in Russia last month but retired in Barcelona with an engine failure.