Anthony Joshua is ready to add a third title to his growing collection.

A bout between Joshua, who holds the WBA and IBF heavyweight belts, and WBO heavyweight titleholder Joseph Parker has been verbally agreed to for March 31, sources with knowledge of the negotiations told RingTV.com.

ESPN reported Thursday that Eddie Hearn, who promotes Joshua, and Duco Events, which handles Parker, finally agreed to the financial split. Duco Events’ David Higgins told ESPN that Parker will earn between 30-35 percent to Joshua’s 65-70 percent of the pie.

Parker (24-0, 18 knockouts) will be a massive underdog to upend Joshua, widely considered the best heavyweight in the world (Tyson Fury holds the RING championship but has been inactive since a November 2015 victory over Wladimir Klitschko.)

The New Zealand native has failed to impress in his three title fights, distance meetings with Andy Ruiz, Razvan Cojanu and Hughie Fury.

Joshua, meanwhile, has risen to the top of the sport. More than 90,000 fans packed Wembley Stadium to watch Joshua rise off the canvas and knock out Klitschko in the 11th round in a heavyweight title classic that was named THE RING’s 2017 Fight of the Year.

When his fight with Kubrat Pulev was announced (Pulev withdrew with an injury and was replaced by Carlos Takam), Joshua sold out an arena in Wales in a matter of hours and set an indoor attendance record (78,000) for a boxing match.

With his big punch and fast hands, most observers will favor Joshua (20-0, 20 KOs) to extend his perfect knockout record against Parker. However, Higgins swears Joshua has a shaky chin that Parker will expose, and Top Rank’s Bob Arum, who also works with Parker, expressed the same sentiment earlier this month.

Showtime has a first and last right of refusal stemming from Joshua’s expired three-fight deal with the premium U.S. cable network, which began with his title victory over Charles Martin in April 2016 and ended with the Brit’s knockout of Eric Molina later that year.

Joshua’s thrilling victory over Klitschko was televised live by Showtime and on tape delay by HBO after an agreement was ironed out. Klitschko had a working arrangement with HBO.

And then Showtime was forced to match an aggressive bid for Joshua’s fall title defense against Takam.

Now, Showtime must enter talks once again to televise Joshua’s fight with Parker. There’s growing sentiment in the boxing industry that Joshua will join HBO following his next fight, when he’s free and clear.

Hearn has a budding relationship with HBO, with the network traveling to Monaco to televise the British promoter’s card featuring Dmitry Bivol’s first-round knockout of Trent Broadhurst, and then also picked up the rights to the unification bout between Ryan Burnett and Zhanat Zhakiyanov.

And when Hearn signed his first American fighter, Daniel Jacobs, HBO quickly consummated an exclusive deal to televise the middleweight contender’s fights. The thought, all along, was that HBO was cozying up to Hearn in an attempt to steer the biggest star in boxing across the aisle.

If Joshua does head to HBO, that could throw a wrench into plans to put together the biggest fight in boxing: Joshua vs. Deontay Wilder, who is aligned with Showtime.

“We’ve made it very clear that this is a Showtime event,” Showtime Sports general manager Stephen Espinoza said. “We’ve spent literally tens of millions of dollars over the last few years developing both Wilder and Joshua here in the U.S. market. We’ve done everything to get them from to no awareness to where it’s arguably the biggest fight in the sport.

“So we’re not going to lose that. We’re confident that our partners on both the Joshua side and the Wilder side understand and respect that. It doesn’t mean things can’t happen, other networks can jump in, but when you’ve spent 20, 30 million dollars, maybe more developing these two guys, I’m confident that our business partners are going to recognize that and say ‘you get the payoff as well.'”

Mike Coppinger is the Senior Writer for RingTV.com. Follow him on Twitter: @MikeCoppinger