Phil Mickelson has withdrawn from next week's PGA Championship, passing up the opportunity to defend his title.

The embattled 51-year-old registered to enter the field, and his name was on the list when the PGA of America announced the field Monday. But Mickelson's representatives said last monththat he was not sure when he would return to golf.

"We have just been informed that Phil Mickelson has withdrawn from the PGA Championship," the PGA of America said in a statement Friday. "Phil is the defending champion and currently eligible to be a PGA Life Member and we would have welcomed him to participate. We wish Phil and Amy the very best and look forward to his return to golf."

Mickelson came under fire in February for remarks he made about a Saudi-financed upstart golf league, now known as the LIV Golf Invitational Series. The six-time major champion told author Alan Shipnuck that the Saudis were "scary (expletives) to get involved with" with a "horrible record on human rights," but he intended to work with them anyway in an attempt to gain leverage with the PGA Tour on financial matters.

After issuing a mea culpa in February, losing multiple sponsors and saying he needed "time away" from the sport, Mickelson went silent and did not play in the Masters. He last played at the Saudi International in February and hasn't played on the PGA Tour since the Farmers Insurance Open in January, where he missed the cut.

Mickelson also registered for the U.S. Open and the first LIV Golf event, both in June. The PGA Tour rejected its members' waiver requests to play in the LIV Golf debut in London earlier this week.

Seth Waugh, CEO of the PGA of America, said on the "5 Clubs Conversations" podcast this week that he had talked to Mickelson about when he might want to return to the course.

"I think he's trying to figure out when the right time is for him," Waugh said. "I think the game is trying to figure out the right time for him, too. How long is enough? And is he ready mentally and physically to do it?"

Mickelson became the oldest major winner in the history of the sport last year when he improbably won the PGA Championship at Kiawah Island in South Carolina at 50 years, 11 months and three days old.

Mickelson's withdrawal would mean that South African Charl Schwartzel, the first alternate, would replace him in the field. Earlier Friday, Harris English withdrew from the event as he continues to recover from hip surgery. He was replaced by Kramer Hickok.

The PGA Championship will be played May 19-22 at Southern Hills Country Club in Tulsa, Okla.