Devin Haney said he is "not racist" and rejects "discrimination of any kind" after saying during an interview that he would "never lose to a white boy".
American Haney made the initial comment when asked about fighting Ukrainian unified lightweight world champion Vasyl Lomachenko.
The 21-year-old, a former WBC champion, was widely criticised on social media.
Haney later said he and WBC president Mauricio Sulaiman had a "very positive conversation".
Responding to a viewer on 78SPORTSTV who said they hoped he would "end the hype of Loma", Haney said: "I'll tell you this. I will never lose to a white boy in my life. I don't care what nobody got to say.
"Fight a white boy 10 times, I'm going to beat him 10 times."
Fellow American lightweight Ryan Garcia tweeted: "We should all respect everyone from every race and see who the best man is!
"I respect Devin Haney and I believe he didn't mean this with racist intent but let's all respect each other for the love of the sport."
Haney later sent two posts on social media.
The first said: "I'm not racist and I never will be a racist. I'm chasing greatness."
He then posted: "I just had a very positive conversation with Mauricio Sulaiman, president of the WBC, and confirmed to him directly my commitment to be a role model and my absolute rejection of discrimination of any kind."
Haney held the WBC lightweight title last year but was declared 'champion in recess' because of injury and has been linked with fights against Lomachenko and Britain's Luke Campbell.
In 2008, American Bernard Hopkins said he would "never let a white boy beat me" before facing Joe Calzaghe, but lost a unanimous decision.