Nico Rosberg says he is not about to crumble mentally after Mercedes team-mate Lewis Hamilton recorded his fourth straight win.
Englishman Hamilton, world champion in 2008, took the championship lead with victory in Spain on Sunday and has won every race he has finished this year.
Rosberg, who finished a close second, said: "Break me down mentally? I think he will struggle with that one.
"He has the momentum. There is no way round that. I have to try to break it."
The two are in a private battle for the championship, despite the hopes of Red Bull and Ferrari that they might erode the huge performance advantage of the Mercedes.
Hamilton leads by three points, having now made up the deficit he incurred by retiring from the season-opening Australian Grand Prix.
"Bit by bit, I am banging on that door," said Hamilton, who admitted his German team-mate was "strong mentally".
He added: "I cannot remember the last time I was in the lead of a championship. If the races are always going to be like that, it is going to be a really long race."
Mercedes have won all five races this season and the team are allowing Hamilton and Rosberg to race freely for victory.
The two drivers say they can maintain a good relationship despite admitting that the "tension" of their fight was high.
Both pointed to the fact that they were title contenders as karting team-mates when they were teenagers without falling out.
Rosberg said: "The advantage we have is that we have done it before, when we were 14, and it is so funny because it is like deja vu all day long.
"Back then we had discussions, debate but always... life goes on, discuss it and life goes on, so that helps, yeah."
Spain was the second race out of the last three in which Hamilton has won despite Rosberg being the quicker driver.
Rosberg trailed Hamilton in the first stint of the race and then switched to a different tyre strategy so he would be on the faster tyre in the final stint, just as he had in Bahrain last month.
He caught Hamilton on the penultimate lap but was unable to pass.
"I wasn't close enough, but next lap I would have been," said Rosberg. "Unfortunately that was it, so a bit gutted. Still, second place. It's still close in the championship and many more races to go."
Hamilton admitted Mercedes would maintain their advantage for some time but refused to rule out others catching them up later in the season.
"At the rate the team's going, we're looking strong for at least a few more races," he said.
"It's by no means easy for me because I've still got a massive challenge with Nico. It's still so close - a long, long way to go.
"I've got a bit more time to find in this car, so I'm going to work on it."