LeBron James has weighed in on Serena Williams' US Open controversy by showing support for the tennis star.

Williams argued earlier this month that she had been treated differently by umpire Carlos Ramos than a man would have been in the same situation.

She was issued a code violation for what umpire Ramos deemed to be coaching from Patrick Mouratoglou, irritating the 23-time major champion, who insisted she was not cheating during her loss to Naomi Osaka in the final.

Williams was given a penalty after smashing her racket and was then docked a game after calling Ramos a "liar" and a "thief".

In an interview with The Hollywood Reporter, James praised Williams for how she handled the situation and explained how she is fighting for equality.

"What we all have to understand is what she is fighting for is bigger than just that match," James said.

"She is fighting for equality — always having to win more, more, more, just to feel equal. Being an African-American woman playing in a predominantly white sport, she's dealing with so much more. I have no idea what was going on in her head, but I feel that struggle."