(Reuters) - Five-times major champion Phil Mickelson has declared the Oakmont Country Club, the venue for next week's U.S. Open, as the toughest golf course he has ever played.

“I played Oakmont the last two days. It truly is, I think, the hardest golf course we’ve ever played,” Mickelson told reporters in Memphis ahead of the FedEX St. Jude Classic.

“They let the rough grow long -- if it’s wet they’ll leave it like that, if it’s dry they’ll thin it out because less balls will hit the fairway.”

Oakmont is known as a stern test that balloons scores.

The last time it hosted a U.S. Open in 2007, Argentine Angel Cabrera won with a five-over total of 285. Mickelson, 45, will bid for his maiden U.S. Open trophy after finishing runner-up six times. “A lot of golf courses, when it challenges you tee to green the way Oakmont does, it usually has a little bit of a reprieve on the greens,” Mickelson said.

“(But) you really don’t at Oakmont, they are some of the most undulating, fast, difficult greens to putt.”

(Writing by Jahmal Corner; Editing by Ian Ransom)