After news broke last week that he had signed his side of a deal for a potential fight against Floyd Mayweather, Conor McGregor has tweeted an image of himself training in the boxing ring. The tweet was captioned with a challenge, bordering on an insult, to Mayweather.

The tweet comes as reports circulate that UFC President Dana White will begin negotiations any day now with Mayweather’s team to complete the deal. Anticipation and expectation for a fight between UFC Lightweight champion McGregor and retired boxing legend Mayweather has been brewing for months. Retirement won’t stop Mayweather from signing the deal, though; he’s already stated that he’s willing to return just to fight McGregor.

As fans continue to have high hopes for a McGregor vs Mayweather bout, there’s bound to be plenty more news and challenges from both sides to come, so stay tuned!