Unified heavyweight world titlist Anthony Joshua likely will face Kubrat Pulev, one of his mandatory challengers, after a deadline to make a deal was extended.

The IBF, which ranks Pulev as No. 1 contender, has given Joshua promoter Eddie Hearn of Matchroom Boxing and Pulev co-promoters Top Rank and Epic Sports an extension of what was originally a Jan. 11 deadline. They now have until Jan. 31 to make a deal before it would call for a purse bid.

John Wirt of Epic Sports told ESPN on Monday that negotiations slowed during the holidays but they are now getting close, which is why they asked the IBF to extend the deadline for a purse bid.

After telling IBF president Daryl Peoples they were "making huge progress," the deadline extension was OK'd.

"We are very close in my opinion, but the real issue is everyone's trying to vet offers [from sites] that are coming in from all over," Wirt said. "The only continents not in play to my knowledge are Antarctica and Australia."

If the sides do not make a deal the IBF will schedule a purse bid to determine the promotional rights, though the camps can continue to negotiate until 15 minutes before the bids would be unsealed. Joshua would get 65 percent of the winning bid and Pulev would get 35 percent. Any bid would likely be worth tens of millions of dollars.

Joshua also has been ordered to make his WBO mandatory defense against Ukraine's unbeaten former undisputed cruiserweight world champion Oleksandr Usyk (17-0, 13 KOs), who turned 33 on Friday. He vacated the cruiserweight titles and made his heavyweight debut with a seventh-round knockout of Chazz Witherspoon on Oct. 12 in Chicago. Usyk is co-promoted by Hearn and likely would take a second fight at heavyweight while Joshua goes through with the bout against Pulev, which would take place in the spring.

Joshua (23-1, 21 KOs), 30, of England, lost his three major world title belts when he was knocked out in the seventh round in a shocking defeat to Andy Ruiz Jr. on June 1 in his United States debut in New York. But Joshua regained the belts on Dec. 7 with a one-sided decision in a rematch with Ruiz in Diriyah, Saudi Arabia. Soon after winning the rematch, Joshua was ordered to make his mandatory defenses.

Pulev (28-1, 14 KOs), 38, of Bulgaria, has won eight fights in a row since challenging then-unified heavyweight world champion Wladimir Klitschko in November 2014 and getting knocked out in the fifth round.