"We thought this was a done deal but it quickly fell apart when Tyson’s people declined all offers,” Kris Lawrence said.

"We were negotiating in good faith all along and it appears we just ended up wasting our time."

As we previously reported, 54-year-old Tyson announced on his podcast last week that he'll be returning to the ring on May 29 in a massive event at Hard Rock Stadium in Miami.

Tyson didn't name his opponent -- but all signs pointed to his old nemesis, 58-year-old Evander Holyfield.

Now, Evander's camp confirms the two sides were in serious talks -- "intense negotiations for several months" -- but the deal ultimately went south.

"Team Holyfield sincerely believed a deal was imminent, especially after the Hard Rock threw its support behind the project, and there were multiple other offers conveyed to Team Tyson," Holyfield's camp said in a statement.

"However, Team Tyson’s demands recently became untenable, and not what Mike Tyson had originally agreed on in direct conversations with Holyfield."

Our sources tell us ... Evander claims he personally spoke with Mike on the phone early on in negotiations and they agreed to a 50/50 split on profit.

But, things changed ... with Evander's camp claiming Team Tyson simply wanted a bigger cut.

Holyfield's team says they tried to make a deal in which Tyson would get a guaranteed $25 mil for the fight -- but Mike turned it down.

Now, it seems both sides are at loggerheads -- and willing to walk away from the deal.

Our sources on the Holyfield side tell us Evander still wants to fight -- if Mike's people will come back to the table with a better offer.

So, there's still hope ... but right now, it's not looking good.