Jason Day has admitted he is feeling the pressure of going into the US Open as the top-ranked golfer in the world.
MORE: Day: Spieth should be bothered by my success
The Australian has been battling with Jordan Spieth for number one status in recent weeks and the 28-year-old has the edge over his Texan rival ahead of the second major of the year at Oakmont.
But Day, who has been suffering from a cold in the days leading up to the opening round on Thursday, revealed he is feeling the strain.
"I've never been more stressed in my life than I am right now," Day told a pre-tournament press conference.
"Your attitude has to be on point for majors. If you're going to have a bad attitude, you might as well not tee it up. I'll be ready come Thursday."
Day, whose solitary major tournament win to date came at the 2015 USPGA Championship, added: "I'm driven to win tournaments. Ten tournaments that I've won is not enough. I need to win more.
"I want it right now. I want it more than anything in the world."
The Australian gave an insight into his plans for the Oakmont course, revealing he will only use his driver on the tee of four or five holes.
"I could hit it all day, but that would be the worst game plan in the world," he said.