Conor McGregor has turned down Dustin Poirier's bid to compete at 170lb this summer.
The rivals are scheduled to clash at lightweight in Las Vegas on July 10 to resolve their six-year rivalry, which currently stands at one win each.
After fighting at 145lb in 2014 and 155lb in January, Poirier proposed they add another 15lb to their frames for UFC 264, according to The Mirror.
McGregor, who has been targeting welterweight champion Kamaru Usman, refused, clearly saying, "No."
McGregor and Poirier had planned to fight at 170lb earlier this year, but UFC president Dana White turned them down.
Poirier went on to defeat his opponent in the second round and has now committed to a trilogy contest rather than a fight for the vacated lightweight belt.
That will be on the line next month as Michael Chandler takes on Charles OIiveira at UFC 262.
Meanwhile, McGregor spent the weekend shouting out Usman both before and after the Nigerian knocked out Jorge Masvidal in the second round of their rematch.
McGregor has recently said that he intends to fight at 170 pounds in order to add a third belt to his set, but he has only faced Nate Diaz and Donald Cerrone at that weight.
On Sunday, he tweeted, "I'm a block at 170 men. Give me until the end of the year at this 155 weight. I'll get the strap and then go up again."
McGregor has long planned to compete at least three times this year, and he hopes success in his rematch with Poirier would propel him to a title shot.
And Chandler assumes the Dubliner would win over Poirier and be the foe for his first title defense.
“Most certainly, I'll be facing Conor McGregor or Dustin Poirier next UFC 264 Live, whoever wins the fight,” he told ESPN. “I believe it'e Conor... Conor, I believe, has a few little items he can do to win the battle. Conor McGregor, I believe, sometime later this fall or winter, although that is potentially wishful thinking.
“If it's Dustin Poirier, I'm pumped for the chance as well. I believe I line up well against Dustin Poirier than I do with a number of other guys in the division.
"That's why I called for the war right away...." If I had to bet, I'd say Conor. I believe he makes any slight changes and wins the trilogy – at least, that's what I believe, and that's who my mind says would win that fight.”