Jorge Masvidal called Conor McGregor a "sissy" - and said he'd "take the head" of the Irishman.
Masvidal was speaking at a press conference with Nate Diaz ahead of their November 2 clash in New York.
The American was asked about the prospect of facing McGregor should he beat Diaz.
In response, Masvidal initially referred to his previous claims that UFC president Dana White said a fight between the two would end up with .
Gesturing towards White, who was stood in between him and Diaz at the press conference, Masvidal said: "The man right here said I'm too much man for that dude so don't bring that dude up in my interviews any more.
"He already said it himself so that fight is not available."
But then he appeared to change his tune, and said if he conquers Diaz he would "take everybody's head that's attached to a belt".
McGregor has been called out by Dustin Poirier, who as he plots a route back to a UFC title shot.
And Masvidal said: "What I'm going to do is wait for those two sissies to clear it out, and if God gives me the victory on November 2 I'm gonna take everybody's head that's attached to a belt.
"If somebody says they have a belt I'm coming for it and if it's any one of those two sissies they're gonna get it."
UFC chief White was then asked about a match-up between Masvidal and McGregor.
He said: "Let this fight happen. I don't know, let's see how this works out."
Ten thousand tickets have already been sold for the fight between Masvidal and fellow American Diaz on November 2, which will be the 500th UFC event.
Meanwhile, White appears to have ruled out the prospect of Conor McGregor making his UFC return in Dublin on December 14 - but .
Asked in a Twitter Q&A session when is McGregor going to fight next, White said: "I'm sure you saw his tweet. Conor wants to fight on December 14 in Dublin, but we have a fight in Vegas.
"So if he doesn't fight on that card, he will fight early next year."
