"I don't know; I just don't know the answer to that right now," Mickelson said after his first round at the Valspar Championship. "I'm scheduled to go through qualifying the day after the Memorial [Tournament in Ohio]."
Golfers can earn a spot in the U.S. Open field via qualifying tournaments or 17 different exemptions. Mickelson will try to earn a spot via final qualifying on June 7.
The 50-year-old currently cannot qualify through any of the exemptions unless the United States Golf Association grants him a special exemption, which have not yet been determined.
Mickelson could hypothetically wind up in the top 60 of the Official World Golf Ranking by May 24 or June 7 and earn a bid that way, but he's currently ranked No. 113.
This year's U.S. Open is at Torrey Pines Golf Course in La Jolla, California, from June 17-20.
The San Diego native has played in the tournament every year since 1990 except for in 1993 and 2017. The five-time major winner has never won the event, but he does have six runner-up finishes and 10 top-10 results.