The biggest heavyweight boxing championship unification in years appears one major step closer to becoming a reality in 2018.  

Unbeaten WBC titleholder Deontay Wilder has accepted an offer from unified champion Anthony Joshua's promoter, Eddie Hearn of Matchroom Sport, for a two-fight deal which includes a first meeting this fall in Joshua's home of England. The deal, however, has not yet been signed.

Wilder (40-0, 39 KOs) revealed the news Monday on social media. Shortly after, his co-manager Shelly Finkel confirmed to multiple sites that the offer includes a rematch in the United States.

"We have agreed to the terms that Eddie has put out to us for a fight in the U.K.," Finkel told ESPN. "Deontay has accepted his terms to fight in the U.K. Deontay sent an email to Joshua [Sunday] night and I sent one today to Barry Hearn and Eddie telling them that we officially accept the offer to fight under the terms they gave us and to send us the contract."

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Joshua (21-0, 20 KOs), who holds the WBA, WBO and IBF titles and has risen over the past year to become the biggest star globally in the sport, turned down a recent $50 million offer from Wilder's team, setting off a confusing stretch of public negotiating. The two sides continued to speak, however, including an in-person meeting last week in New York between Finkel and Matchroom Sport founder Barry Hearn. 

Finkel told World Boxing News on Monday that Wilder agreed to Joshua's terms on the latest contract offer and has now given Hearn 48 hours to send the official contract. 

"If for any reason Anthony changes his mind and wants to fight in the U.S, the $50M offer we have made to him is still there," Finkel said. "It's now in Joshua's court. It will take place in the U.K. either September or October according to Eddie Hearn.

"They gave us an offer, we were hoping they'd accept the U.S offer instead because there's so much money but instead, since they haven't, we've decided that if you don't want $50 million then we're willing to come the U.K. and take your offer. Hopefully, we'll get an answer in the next day or two. Deontay wrote to Joshua and said 'Hey, I accept your offer, let's fight in the U.K.'"

The fight, pairing unbeaten sluggers at the peak of their physical primes, would be one of the biggest the sport could make and the most important the division has seen in 15 years. 

Joshua, who won his first world title by stopping Charles Martin in 2016, scored his biggest victory to date the following year by rising from the canvas to knock out former champion Wladimir Klitschko in front of 90,000 spectators in London. In March, the 28-year-old added a third world title by outpointing WBO champion Joseph Parker in Wales. 

Wilder, 32, a native of Alabama, has made seven defenses -- all by knockout -- of the title he won from Bermane Stiverne in 2015. His most recent victory, a comeback knockout of Luis Ortiz in March, was also his most impressive.