Jack Nicklaus says he turned down an offer worth more than $100m to be the face of the Saudi-backed LIV Golf Invitational Series that is hoping to challenge the PGA Tour.

Nicklaus, who counts a record 18 major titles among his 73 PGA Tour wins, said in an article on the Fire Pit Collective website that organisers of the series asked him to spearhead the big-money circuit.

"I was offered something in excess of $100m by the Saudis, to do the job probably similar to the one that Greg (Norman) is doing," Nicklaus was quoted as saying.

"I turned it down. Once verbally, once in writing. I said, 'guys, I have to stay with the PGA Tour. I helped start the PGA Tour'."

World Golf Hall of Famer Norman serves as chief executive of LIV Golf and the Australian came under fire last week when he downplayed the 2018 killing of Saudi Arabian journalist Jamal Khashoggi, saying: "We've all made mistakes."

The LIV Golf Invitational Series, which will feature an individual and team concept, is scheduled to hold its inaugural event season 9-11 June at Centurion Club outside London with a total prize purse for the eight-event season of $255m.

The PGA Tour last week denied the conflicting event releases for those members who sought to play at Centurion that same week as its RBC Canadian Open in Toronto.

Six-times major champion Phil Mickelson, who stepped away from the game in February amid fallout from comments he made regarding a Saudi-backed golf league, is among the players who had requested releases into the first LIV Golf event.

Mickelson's public image took a hit when the author of an unauthorised biography on the long-time fan favourite said the golfer told him he was willing to look past Saudi Arabia's human rights record to gain leverage with the PGA Tour.

Saudi Arabia's government has denied accusations of human rights abuses and Mickelson later apologised for the comments, which he claimed were off the record, and then said he planned to take time away from the sport.

"My advice to Phil? My advice to Phil would be to be patient," Nicklaus said in the report. "The world is a very forgiving place. But he's the one he has to decide where he wants to play and what he wants to do."