Unified middleweight world champion Gennady Golovkin has said over and over that he wants to fight on May 5 despite the cancellation of his rematch with Canelo Alvarez, and the GGG team and HBO are proceeding as though he will face Vanes Martirosyan that night at the StubHub Center in Carson, California.

But if GGG does face Martirosyan, it likely will cost him one of his three major title belts.

The fight is not yet signed, but Golovkin promoter Tom Loeffler and Don King, Martirosyan's promoter, are close to finalizing a deal for the bout. But while the California State Athletic Commission has approved Martirosyan as an opponent and the WBC and WBA, whose world titles Golovkin holds, have agreed to the sanction the title fight, the IBF -- which also recognizes GGG as its world champion -- told Golovkin on Tuesday that it won't approve the bout and that if he fights Martirosyan it would likely strip him of the title.

IBF attorney Linda P. Torres sent a letter on Tuesday to attorney Ron DiNicola, who represents the Golovkin side, and Alex Dombroff, the attorney for promoter Lou DiBella, who promotes IBF mandatory challenger Sergiy Derevyanchenko, outlining the reasons for the IBF's refusal the grant approval for Golovkin-Martirosyan, a source with knowledge of the letter told ESPN.

Derevyanchenko is pressing for his mandatory shot at Golovkin, which is due now that Alvarez is out of commission following two positive tests for the banned performance-enhancing drug clenbuterol in random urine tests conducted by the Voluntary Anti-Doping Association in his hometown of Guadalajara, Mexico, in February.

Only two of Gennady Golovkin's three world title belts will be on the line when he fights Vanes Martirosyan May 5. Nick Potts/PA via AP

The positive tests caused the fight to be canceled, and Alvarez is under temporary suspension by the Nevada State Athletic Commission. He faces an extension of his punishment at a commission hearing on Wednesday. It has left Loeffler scrambling to finalize another fight for Golovkin.

In the letter, Torres outlined the reasons for the IBF's refusal the grant approval for Golovkin to defend against Martirosyan. The IBF's reasons for refusing the approve the fight are same reasons why the proposed bout with Martirosyan (36-3-1, 21 KOs), 31, a 2004 U.S. Olympian from Glendale, California, has received so much criticism from boxing fans and media: Martirosyan is coming off a loss, he is a junior middleweight who would be moving up in weight and he has not fought in two years.

If Golovkin goes ahead with the bout against Martirosyan, the IBF said it would invoke its rule 5.H, which states, "If a champion participates in an unsanctioned contest within his prescribed weight limit, the title will be declared vacant whether the champion wins or loses the bout. The championships committee, with the approval of the (IBF) president, will then establish a new champion in that division in accordance with the procedures established and prescribed in these rules."

The IBF rules do provide Golovkin with the ability to seek an exception to the mandatory bout, but the IBF's reasons for not approving the fight in the first place would not bode well for him to get the exception granted. Loeffler acknowledged the letter from the IBF and told ESPN that Golovkin plans to fight May 5 and said their side will seek an exception, adding that he hopes the IBF will grant one.

"Gennady is a proud champion of the IBF and, as a unified world champion, he looks forward to remaining champion for a long time and defending his middleweight titles many more times," Loeffler said.

For years, Golovkin's stated goal has been to unify the four major middleweight world titles. He is three-quarters of the way there. It would go against everything he has said if he allowed himself to be stripped for the sake of facing Martirosyan in a fight for which he will paid a fraction of the money he has been making.

The rematch with Alvarez would have been May 5 on HBO PPV at the T-Mobile Arena in Las Vegas -- the same outlet and venue as their controversial draw in September. That fight sold about 1.3 million units and generated the third-highest gate in boxing history -- more than $27 million -- and Golovkin made an eight-figure payday.

Golovkin was looking at another bonanza for the rematch; however, the fight with Martirosyan, on regular HBO at the StubHub Center, would pay him a very low seven-figure payday.

But Golovkin said he wants to be active and hopes to face Alvarez in September in a rematch, as long as Alvarez is eligible to fight.

Once Golovkin (37-0-1, 33 KOs), 35, a Kazakhstan native fighting out of Santa Monica, California, files for the exception, Derevyanchenko (12-0, 10 KOs), 32, a 2008 Olympian from Ukraine, is allowed to file an opposition to the request, at which point the IBF would review the case of each side and make a determination. The two sides also could reach some sort of compromise and offer a united front to the IBF.

Either way, time is of the essence; May 5 is less than three weeks away.