Former world champion Lewis Hamilton has likened his tussle for this season's Formula One title with Mercedes colleague Nico Rosberg to a game of poker.
Rosberg currently has an 11-point lead over his British team-mate with eight races of the season remaining and their rivalry has become increasingly heated over the course of the year.
Hamilton disobeyed team orders by refusing to allow Rosberg to pass him during last month's Hungarian Grand Prix, and he admits that there is an edge to his relationship with the German.
"The battle does feel a lot more intense this year," said Hamilton, who was speaking at an event for Mercedes' team partner Puma.
"When I was racing against Kimi Raikkonen (in 2007) and Felipe Massa (in 2008), they were in a different team and their cars had different strengths and weaknesses to my car and, in my team, it was just me that was really competing with them.
"Now I'm racing against a guy who has the same car as me. We both have access to exactly the same data and feedback, so it is really hard to try and be ahead.
"It's a little bit like playing poker. You have a set of cards and the other guy is not supposed to know what you've got, but Nico and I can see each other's cards, so then it's more difficult to beat each other."
While the relationship between the pair has appeared strained at times, Hamilton says that he is enjoying the competition.
"It is definitely more challenging (than competing against someone from another team), because you have to find ways to create small margins," said the 29-year-old, who won the world championship in 2008.
"And so what you do is bring your skills, things that you've learnt, things you can put into the mix. And you always have to move forward.
"You can't just be good and that will be enough -- you have to keep pushing the boundaries, because every time you take a step forward the other guy makes an equal step, so you have to keep doing it."