American Ryan Harrison will be investigated after allegations of "racial prejudice" during a match against Donald Young, the Association of Tennis Professionals has confirmed.
The chair umpire intervened during the pair's first-round meeting at the New York Open on Monday.
"I'm shocked and disappointed to hear you [Harrison] tell me how you really feel about me as a black tennis player," Young tweeted afterwards.
Harrison denies Young's claims.
Harrison, 25, who won the match 6-3 7-6 (7-4), posted that any video or audio from the match would "100% clear me".
"The accusations made by Donald Young tonight following our match are absolutely untrue.