Serena Williams felt she produced the best performance of her comeback so far in trouncing sister Venus 6-1 6-2 at the US Open.

A six-time women's singles champion at Flushing Meadows, Serena displayed sensational form during a one-sided third-round clash under the lights of Arthur Ashe Stadium on Friday.

Venus labelled Serena's display "untouchable" and the younger sibling – who made the Wimbledon final this year after returning from the birth of her first child – said: "I think it's by far the best match I ever played against her in forever [a long time]. I don't know about ever, ever. It probably was.

"I played much better tonight than I have since I started this journey on my way back."

Asked how she maintains such a high level when facing Venus, Serena added: "It's just about focusing on each point. It is my sibling, but it's [also] one of the greatest players of all time, by far the greatest player I've ever played against.

"It is definitely something that you have to put aside if you're playing against someone like her.

"It feels good for the match to be over with. Win or lose, it just feels good that that's done.

"For me it takes more mental energy than physical [playing Venus]. It's not easy, but it is what it is."

There was an early injury scare for Serena, who rolled her right ankle in the second game and took a medical timeout.

"I roll my ankle often. The tape on it helped a lot. So I just added a lot more secure tape," she explained.

"It didn't bother me at all."

Next up for the 23-time grand slam singles champion is a fourth-round clash with Kaia Kanepi.