Four-time major winner Rory McIlroy offered some of the harshest criticism yet of PGA Tour players who have defected to the rival LIV Golf Invitational Series, saying Wednesday that some are "duplicitous" for backing out of their commitments to the tour.

McIlroy, speaking to reporters at a news conference ahead of this week's Travelers Championship in Cromwell, Connecticut, said he was bothered that some players, including Brooks Koepka, made an about-face after previously pledging loyalty to the tour.

"But am I surprised? Yes, because of what he said previously," McIlroy said. "I think that's why I'm surprised at a lot of these guys -- because they say one thing and then they do another ... I don't understand that, and I don't know if that's for legal reasons or if they can't -- I have no idea. But it's pretty duplicitous on their part to say one thing and then do another thing."

When McIlroy was asked whether he was referring to Koepka's comments from two years ago or a week ago, he said, "The whole way through. The whole way through, in public and private, all of it."

On Tuesday, Koepka became the latest PGA Tour player to join the LIV Golf circuit, which is being fronted by two-time Open winner Greg Norman. Koepka will compete in the first LIV Golf event in the United States next week in Portland, Oregon.

Last week, Koepka, who is ranked 19th in the Official World Golf Ranking, criticized reporters for asking him questions about LIV Golf, saying it cast a "black cloud" over the U.S. Open.

"I'm here at the U.S. Open," Koepka said. "I'm ready to play the U.S. Open, and I think it kind of sucks, too, you are all throwing this black cloud over the U.S. Open. It's one of my favorite events. I don't know why you guys keep doing that. The more legs you give [LIV Golf], the more you keep talking about it."