Johnson was speaking at a press conference at Centurion Club, outside London, ahead of the opening event of the Saudi-backed breakaway tour, which starts on Thursday.
World number 15 Johnson said in February he was committed to playing on the US PGA Tour, which has refused releases for members to play in LIV Golf’s opener.
“I’m very thankful to the PGA Tour and everything that it’s done for me… but this is something I felt was best for me and my family and I’m very excited about playing,” he said.
Johnson said it was difficult to predict the consequences of his decision to play on the breakaway tour.
“Right now, I’ve resigned my membership from the Tour. I’m going to play here for now and that’s the plan,” he added.