Mickelson is set to play competitive golf for the first time since February ©Getty Images

Six-time major championship winner Phil Mickelson has confirmed that he will play at the newly-founded LIV Golf Invitational Series when play commences on Thursday.

The 51-year-old American, who has not played for over four months, released a statement via his Twitter profile announcing his return at the Saudi-backed league.

He also confirmed his intention to compete in all the golf majors including the upcoming US Open, which is due to start on June 16. 

However, he made no reference to participating in PGA Tour events.

Mickleson said: "I am ready to come back and play the game I love but after 32 years this new path is a fresh start...

"I also love the progressive format and think it will be exciting for fans. 

"Just as importantly, it will provide balance, allowing me to focus on a healthier approach to life on and off the course."

Mickelson is one of the most decorated players in modern golf history with 45 PGA Tours wins, three Masters titles, two PGA Championship titles and one Open Championship.

The California native chose not to try and defend his PGA Championship title last month, after comments he made about the new breakaway competition.

It has been heavily criticised for the origin of its funding, Saudi Arabia's Public Investment Fund, and for the enormous purses being offered to players, with the the total prize money believed to be around $255 million (£198.5 million/€233.7 million).

Fellow American Dustin Johnson will also be playing at the LIV Series after resigning from the Tour, despite previously voicing his commitment to the organiser.

"It's hard to speak on what the consequences might be but I've resigned my membership of the Tour and that's the plan for now", Johnson said at a press conference. 

The pair are part of a 48-man field that are confirmed to be playing in the series, which includes 2017 Masters winner Sergio Garcia.  

The first event of the LIV Golf Invitational Series will be played at the Centurion Club in St Albans, England, with seven more events scheduled to follow this year.