Canelo Alvarez and his promoter, Golden Boy CEO Oscar De La Hoya, were willing to compromise. Gennady Golovkin promoter Tom Loeffler was, too.

But in the end, Golovkin, the unified middleweight world champion, was unwilling to come off his demand for parity in a proposed Sept. 15 rematch, and the already fragile negotiations collapsed on Tuesday with De La Hoya ending talks and sending a formal offer to middleweight contender Daniel Jacobs to fight Alvarez on Sept. 15 in an HBO PPV main event at the T-Mobile Arena in Las Vegas.

"He's stubborn and wanting 50-50, and it's not going to happen," De La Hoya told ESPN about Golovkin. "The Canelo train has left the station."

De La Hoya said he had Golden Boy Promotions president Eric Gomez contact Matchroom Boxing promoter Eddie Hearn, Jacobs' promoter, on Tuesday afternoon to start negotiating the fight.

"So there's a deal on the table for Daniel Jacobs to fight Sept. 15 against Canelo," De La Hoya said. "Eddie loves the idea. He loves the fight. Daniel Jacobs loves the fight, and we love the fight as well. So we're just moving forward and making sure that Canelo has the toughest dance partner possible for Sept. 15."

Daniel Jacobs, left, gave Gennady Golovkin the toughest fight of his career when they met in March 2017. Now, Canelo Alvarez promoter Oscar De La Hoya is in talks with Jacobs' camp regarding a proposed HBO PPV main event in Las Vegas on Sept. 15. AP Photo/Frank Franklin II

Hearn, speaking to ESPN from his home in England, said he was pleased to hear from Gomez and hopes to finalize the fight.

"I can tell you that we love the fight," Hearn said. "It's a fight that when I signed Daniel Jacobs he told me he believes he beats Canelo every day of the week. We had a brief conversation with Golden Boy about a week ago or so [when Alvarez-Golovkin negotiations were first on the ropes], and it was hard to tell whether it was part of the plan in the negotiations with Canelo-Golovkin or if they really wanted the fight. We confirmed our interest, and today we received an official offer to fight Canelo on Sept. 15.

"I've taken the offer to Keith Connolly, Danny's manager, Danny. We're extremely interested. Obviously, it's a huge fight."

Hearn said he hoped to make the deal quickly and didn't intend to drag things out.

"It's a first offer, and we are not looking to be difficult, but we know our value in the fight," Hearn said. "We have a guy in Daniel Jacobs who, in my opinion, beat Gennady Golovkin, but in anybody's opinion had a wonderful fight with Golovkin which many couldn't split. In that respect, I see Jacobs as the perfect guy to fight Canelo.

"This is one of the reasons we signed with HBO -- to get this fight. Now we're here. I will push for every dime for my client. At the same time, we realize this is a wonderful opportunity, and we'll do everything we can to make this fight. This is a major, major, major fight for Danny Jacobs. We know the money involved in the fight. We believe it does big pay-per-view numbers."

De La Hoya said he hoped to also wrap it up quickly.

"The deadline is going to be middle of this month because we have to start promoting and lock down everything," he said. "Our sponsors are ready to go, and we want to give the fight fans the best possible fight, and unfortunately GGG didn't budge from his 50-50, so we're moving on."

In March 2017, then-secondary middleweight titlist Jacobs (34-2, 29 KOs), 31, of Brooklyn, New York, met unified world champion Golovkin in a mandatory fight at Madison Square Garden in New York and gave Golovkin the toughest fight of his career.

Although Jacobs got knocked down in the fourth round, he put on a tremendous performance in a debatable decision loss -- 115-112, 115-112 and 114-113 -- to end GGG's knockout streak at 23 consecutive fights.

"Jacobs gave GGG a run for his money. A lot of people thought that he won," De La Hoya said. "I can't say he won't be Canelo's toughest fight. He might be tougher than GGG."

"If GGG ever comes to his senses, we can fight next year if he wants for Cinco de Mayo. I tell you one thing -- the money he would make for Canelo, he now has to fight five or six opponents to make that kind of money. We've moved on." Golden Boy CEO Oscar De La Hoya

Golovkin next faced Alvarez in a September blockbuster -- 1.3 million pay-per-view buys and the third-best gate in history at $27 million -- and they fought to a highly controversial draw that most thought Golovkin won.

After drawn-out negotiations, the rematch was set for May 5 at T-Mobile Arena, but in February, Alvarez twice tested positive for the banned substance clenbuterol in his hometown of Guadalajara, Mexico, in random tests conducted by the Voluntary Anti-Doping Association. Alvarez blamed eating contaminated beef -- a well-publicized problem for athletes in Mexico -- but the rematch with GGG was canceled and Alvarez was suspended for six months by the Nevada State Athletic Commission.

Golovkin was incensed. He verbally attacked Alvarez (49-1-2, 34 KOs), 27, of Mexico, and accused him of using performance-enhancing drugs in their first fight, even though he had no evidence. Golovkin (38-0-1, 34 KOs), 36, a Kazakhstan native fighting out of Santa Monica, California, went on to fight anyway on May 5 in a hastily arranged fight with massive underdog Vanes Martirosyan that was moved to the StubHub Center in Carson, California, and taken off pay-per-view and placed on HBO. And instead of earning the $20 million or so he would have made for the rematch with Alvarez, he made around $1 million to fight Martirosyan, whom he knocked out in the second round in a division record-tying 20th consecutive title defense.

After the fight, Golden Boy and Loeffler tried to put the rematch back together for Sept. 15, and they had come to terms with Alvarez, who cleared a major obstacle by signing up for year-round VADA testing, set to receive 65 percent of the revenue and Golovkin 35 percent. But the deal was not signed, and Golovkin had a change of heart on the terms he wanted.

"What people are not understanding is I am not going to come off my demands for the rematch," De La Hoya said. "The fact that GGG is stubborn on a 50-50 split, and it's ludicrous. It's never going to happen. He wants 50-50, and it's never going to happen. We had already come to terms, and they had the contracts a long time, several weeks, and now he wants 50-50?"

De La Hoya said their side was willing to compromise and move to 60-40 after Alvarez got a favorable 70-30 split for the fight last year.

"We were willing to budge, but now I'm fed up with this, and I've decided to move on. So we are talking to Eddie Hearn about Jacobs," De La Hoya said. "Let's make the best deal possible. The deal is on the table for Daniel Jacobs, and hopefully we can get it signed sooner than later so we can start promoting the fight."

Loeffler was surprised to hear that De La Hoya had made an offer to Jacobs when informed by ESPN.

"I spoke to Eric [Monday night], and we were still in discussions, so I think if there's a way to find a solution, we'll try to find it, but I didn't speak to him [on Tuesday]," Loeffler said. "But 50-50 is the position [Golovkin] has taken. Canelo's taken his position. It's our job to figure out if there's a way to make the fight work. All I can say is that those two guys [Alvarez and Jacobs] are guys GGG already beat last year. Canelo would make more in a GGG fight than he will against Daniel Jacobs, so that goes both ways."

De La Hoya didn't make it sound like the Alvarez side was going to reverse course and go back to Golovkin.

"If GGG ever comes to his senses, we can fight next year if he wants for Cinco de Mayo," De La Hoya said. "I tell you one thing -- the money he would make for Canelo, he now has to fight five or six opponents to make that kind of money. We've moved on."