The U.S. Justice Department is investigating whether the PGA Tour broke antitrust law in fighting off the rival LIV Golf circuit, backed by Saudi Arabia.

The PGA Tour confirmed the probe, which was first reported by the Wall Street Journal.

"This was not unexpected. We went through this in 1994 and we are confident in a similar outcome," a PGA Tour spokesman said in an email statement referring to an investigation decades ago by the Federal Trade Commission.

The Journal reported that the government had reached out to players' agents regarding PGA Tour bylaws that limit players' ability to participate in rival golf events.

The $255 million LIV series is being bankrolled by Saudi Arabia's Public Investment Fund (PIF), which critics say is a vehicle for the country to improve its image in the face of criticism of its human rights record.

LIV has lured away major winners including Phil Mickelson, Dustin Johnson, Brooks Koepka and Bryson DeChambeau with huge sums of money, while others like Jordan Spieth and Rory McIlroy have said they plan to stay with the PGA and DP World tours.

The Journal said that the PGA Tour has required golfers who wanted to play in LIV competitions to request releases, and has suspended some who failed to do so.

The Justice Department declined comment on the probe.