American Tennys Sandgren has apologised for writing on Twitter that a visit to a gay club had "left his eyes bleeding".
Sandgren faced questions over claims he was a supporter of the alt-right movement and accused the media of "demonising" him in a pre-prepared monologue following his 6-4 7-6 (7/5) 6-3 defeat to Hyeon Chung in the Australian Open quarter-finals.
The 26-year-old said: "You seek to put people in these little boxes so that you can order the world in your already assumed preconceived ideas
But Sandgren received criticism from Serena Williams on Twitter, who called for Sandgren to apologise to "an entire group of people".
Sandgren wrote on Thursday: "In regards to the gay club tweet from 2012, I used poor and harsh words to describe a bad experience, and is not indicative of how I feel about the people in that community.
"To everyone I offended with that, please accept my apology."
Sandgren's breakthrough at the Australian Open has led to increased scrutiny of his views, and deleted all his messages on Twitter bar one.
After his exit from the Melbourne competition, Sandgren said he would head home to Tennessee to reflect on everything that has happened this fortnight.