Phil Mickelson, who has not played competitively since incendiary remarks he made in support of a Saudi-backed golf league that hopes to rival the established PGA Tour were reported in February, will end his self-imposed layoff later this week by playing in the first event of the upstart LIV Golf circuit.

Mickelson, the winner of six major golf championships including last year’s P.G.A. Championship when he became the oldest golfer to win a major, will be one of 48 players competing for $25 million in prize money when the tournament begins Thursday at the Centurion Club near London. Last week, Dustin Johnson, 15th in the men’s world golf rankings, also agreed to compete on the alternative tour. A report in The Telegraph said Johnson was paid $125 million to join LIV Golf, whose major shareholder is the Public Investment Fund, the sovereign wealth fund of Saudi Arabia.

The breakaway tour has also promised hefty appearance fees and a format that guarantees every entrant six-figure payouts.

“This new path is a fresh start, one that is exciting for me at this stage in my career,” Mickelson, whose world ranking has slumped to 72nd, wrote on Twitter Monday. “I fully realize and respect some may disagree with this decision and may have strong opinions and I empathize with that. I have a renewed spirit and excitement for the game,” he added.

Mickelson’s announcement will most likely lead to his suspension from the PGA Tour, which has paid Mickelson more than $94 million in tournament earnings for 30 years. Jay Monahan, the PGA Tour commissioner, has said players who choose to play LIV Golf events will be subject to discipline that could include suspensions or lifetime bans.

Mickelson, with a reputation as a golf firebrand, might relish a court challenge to the PGA Tour’s right to ban him. Monahan has not flinched when asked if he had the authority to discipline players in that manner, insisting that the tour’s lawyers believe any punishment handed to golfers who play for the rival tour will withstand legal scrutiny.

Mickelson, one of the most recognizable golfers of his generation, drew heavy criticism after he acknowledged Saudi Arabia had a “horrible record on human rights” — including the murder of a Washington Post journalist — but said he was still talking with, and aiding, the new tour because it was a “once-in-a-lifetime opportunity.” Earlier this year, Mickelson, 51, accused the PGA Tour, where he has won 45 times, of “obnoxious greed.” He later said his remarks were “reckless,” but nonetheless several longtime corporate sponsors, including KPMG and Workday, ended their relationships with him.

On Monday, Mickelson wrote: “I want to again apologize to the many people I offended and hurt with my comments a few months ago. I have made mistakes in my career in some of the things I have said and done. Taking time away and self-reflecting has been very humbling.”

The tournament near London is one of eight events this year in the LIV Golf Invitational Series. Early this season, Mickelson competed in three PGA Tour events, missing the cut in two and finishing tied for 30th in the third.

Although a three-time Masters winner, he skipped this year’s tournament. On Monday, however, Mickelson said he intended to play in future major championships. He is currently in the field for next week’s U.S. Open and next month’s British Open.

Greg Norman, the chief executive and commissioner of LIV Golf, who said last week that “free agency has finally come to golf,” praised Mickelson.

“His contributions to the sport and connection to fans around the globe cannot be overstated, and we are grateful to have him,” Norman said on Monday in a statement.

Many of Mickelson’s colleagues on the PGA Tour, including his longtime rival Tiger Woods, have been critical of Mickelson’s adversarial stance toward the tour.

“The viewpoints that Phil has made with the tour and what the tour has meant to all of us has been polarizing,” Woods said last month.

Rory McIlroy, a four-time major winner, called Mickelson’s comments, “naïve, selfish, egotistical, ignorant.”

Last week, McIlroy, who has been outspoken in his disdain for the LIV Golf venture, was dismissive of the catalog of players entered in the tournament to begin Thursday at the Centurion Club.

“I certainly don’t think the field is anything to jump up and down about,” McIlroy said.

But Monday on Twitter, Mickelson was cheerful.

“I’m thrilled to begin with LIV Golf and I appreciate everyone involved,” he wrote.