Serena Williams has revealed that her sister Venus Williams is the one player that she does not want to face in the US Open.

The siblings will play each other for the 27th time after the 33-year-old defeated Madison Keys in the fourth round of the competition in straight sets, while Venus overcame Anett Kontaveit.

"She's the only player in the draw I don't want to play, not only because she's my sister, but because for me she's the best player," Williams told reporters.

"She's beaten me so many times. I've taken a lot of losses off her – more than anybody. She's a player that knows how to win, knows how to beat me, and knows my weaknesses better than anyone.

"We have a very similar game. She's fast, I'm fast. She hits hard, I hit hard. She serves big, I serve big. We had the same coach for a long time. It's like playing a mirror. I have to be really ready."

Serena has beaten her sister in 15 of their 26 meetings.