ERIN, United States (AFP) - Jordan Spieth is bracing for what he believes is the toughest mental battle in golf as he attempts to reclaim his US Open crown at Erin Hills Golf Course.

The 23-year-old Texan has failed to add to his major tally since a spectacular 2015, where he won the Masters and the US Open before narrowly missing out at the British Open and PGA Championship.

A final round meltdown at the Masters last year came to define his 2016 campaign, but Spieth says he is in a positive frame of mind as he aims to repeat his 2015 US Open victory in Wisconsin.

The key, Spieth said, would be conquering the mental challenges thrown up by a tournament portrayed as the toughest test in golf.

"Just dealing with the mental side of the game more than any other tournament," Spieth said of the US Open.

"It's always a physical test. It's a big golf course. It's a tough one to walk.

"You're just putting more effort into each round. But then most of all it certainly tests the mental game more than any other place in golf. And I've witnessed that on both sides of things.

"If you came for a stress free tournament you didn't come to the right place. And we know that going in."

Spieth, who has only one PGA Tour victory to his name this season, is one of the few players in this week's field to have competitive experience of Erin Hills, having played at the venue in the 2011 US Amateur Championship.

Spieth agreed the 7,441-yard layout could often punish excessively aggressive players.

"It can do some weird things to it if you try to do too much out here," he said.

However, he is unmoved by criticism of the dense fescue grass fringing many of the fairways.

"It just depends on where it ends up, what the lie is," he said.

"It's not unplayable. I don't think the golf course is unfair, by any means, because of the fescue."