DUBLIN, Ohio — Phil Mickelson said on Saturday that he would withdraw from the United States Open, the only major championship he has not won, to attend what he considers a more important event — his daughter Amanda’s high school graduation.

The commencement exercises for the Pacific Ridge School are scheduled for midmorning in California on June 15, the day of the Open’s first round at Erin Hills in Wisconsin.

“So there’s just really no way to make it, no matter what the tee time is,” Mickelson said.

He said he had informed Mike Davis, the United States Golf Association’s executive director, on Saturday morning of his plan to withdraw so that alternates in the field can prepare accordingly.

Mickelson said he would hold off on officially withdrawing until a day or two before the tournament started, in case a weather delay or change in the morning commencement ceremony time made it possible for him to be at both.