Mikaela Mayer kicked out at Alycia Baumgardner as tensions spilled over for the final time before the women get in the ring.
The IBF and WBO super-featherweight world champion reacted after the weigh-in for her unification fight against her compatriot, who holds the WBC belt.
The pair have sniped at each other throughout the build-up to Saturday’s fight, which acts as the chief support to Claressa Shields vs Savannah Marshall at The O2.
The winner will immediately rocket up the pound-for-pound rankings, likely closing in on a top-three place, while also positioning them to step up in weight for a mega fight against Katie Taylor.
Tensions have simmered throughout with Baumgardner goading the Olympian for being “spoilt” and “entitled” given her status as a Top Rank fighter.
Both fighters made weight at 9st 3lbs 5oz before Baumgardner appeared to push Mayer, prompting a feisty reaction.
“I didn’t have any arms because I had three belts, so I used my leg,” Mayer told Sky Sports. “All this talk about struggling to make weight is a reflection of what’s going on with this girl.
“She spends too much time in the weight room, she’s struggling. She has to knock me out, she knows that, it’s the only way she’s going to win.
“I’m going to out-box her, she thinks she’s a good boxer but she’s never been in there with somebody like me.”
Mikaela Mayer vs Alycia Baumgardner is live on Sky Sports Main Event, Sky Sports Arena and Sky Sports Showcase on Saturday, coverage starts from 7.30pm