Dustin Poirier created a Twitter firestorm by accusing Conor McGregor of reneging on a $500,000 charity donation

• Dustin Poirier and Conor McGregor are at loggerheads on Twitter.
• The American accused his lightweight rival of reneging on a vow to donate $500,000 to his charity.
• McGregor then said their prospective July 10 trilogy is canceled, and that he'll fight someone else.

Dustin Poirier created a Twitter firestorm by accusing Conor McGregor of reneging on a $500,000 donation to charity.

The UFC rivals fought for a second time in January when the American left McGregor concussed on the canvas after crippling his leg with merciless kicks, and shellacking him against the fence.

Ahead of that bout, the pair had spoken about the positive effect their lightweight fight could have.

The Irishman even pledged to donate $500,000 to Poirier's "The Good Fight" foundation which is an initiative that has dug water wells in Uganda, and purchased school supplies for children in need.

But, according to Poirier, McGregor's donation never came.

"You predicted a donation to my foundation and you and your team stopped responding after the fight in January," Poirier tweeted Monday.

Within hours, McGregor responded by implying Poirier's foundation may not be above board, and had been requesting information about what, exactly, his donation would go toward.

This, he claimed, was information he never received.

"A donation not a debt," McGregor said. "We've been awaiting the plans for the money that never came. I do with all my donations.

"Know where it's going dot for dot. Otherwise it goes walking. As is the case with a lot of these foundations, sadly."

In October, when the fighters first talked about a charity exhibition outside of the UFC, Poirier said McGregor's $500,000 donation would be used "to open a boxing/MMA academy" with additional tuition to help children attain good grades at school.

No further details were given at that time.

As Poirier pursued a third McGregor fight tentatively scheduled for July 10 over a lightweight title shot, it showed McGregor "was right," the 32-year-old said this week.

Replying to McGregor's remark about the difference between donation and debt, Poirier said: "100% never a debt. You offered, we accepted.

"Your team never responded to our emails regarding the process of where funds would be put to work."

He finished by remarking that McGregor will get beaten, "again," on July 10 - a comment that seemed to further irk the Irishman as he called Poirier "inbred" and a "f------ brain dead hillbilly."

He said: "The fight is off. I'm going to fight someone else."

It remains unclear whether this is all pre-fight theatrics, or if McGregor is attempting to back out of his prospective summer showdown against Poirier so he can take on a different challenger.

Regardless, many UFC lightweights voiced their interest in replacing Poirier.

Michael Chandler said he'd be willing to compete on July 10 after he fights Charles Oliveira for the UFC championship in May, Rafael dos Anjos said it would be a "red panty night," and Kevin Lee said he'd be ready for the match, too.

The UFC is yet to comment on the situation, or indeed, but confirmed Wednesday that Poirier and McGregor will complete their trilogy during July's International Fight Week in Las Vegas.