Venus Williams said sister Serena played "untouchable tennis" en route to a thumping 6-1 6-2 victory in their US Open third-round tie.

The much-anticipated encounter under the lights of Arthur Ashe Stadium proved one-sided as Serena – a six-time singles champion at Flushing Meadows – sparkled against her elder sibling.

Perhaps unsurprisingly given the manner of her victory, Serena labelled her performance as the best she had produced since returning to the game after the birth of her first child.

In a news conference on Friday, that comment was put to Venus, who replied: "I think it's the best match she's ever played against me. I don't think I did a lot wrong. But she just did everything right. Obviously that level is definitely where she's going to want to stay during this whole tournament."

"I mean, she played so well, I never got to really even touch any balls. When your opponent plays like that, it's not really anything to be upset about."

"The only thing I maybe could have done was put more first serves in. Even then she returned the first serve really well. Any shot that I hit great, she hit a greater shot."

"She didn't win that match because I just rolled over. She played untouchable tennis."

The 30th professional meeting between the Williams sisters played a significant part in attracting a record single-day attendance of 70,162 to the USTA Billie Jean King National Tennis Center.

Yet Venus passed up the invitation to discuss the enormous impact the pair have had on tennis and the wider world.

"We don't sit around and reflect," she explained. "That's not how you get out here and win these matches, reflecting and looking back. You work hard, look forward. As soon as you beat one person, there's another one standing in front of you."

"At the moment now our main focus is winning these matches. Perhaps when it's all said and done there will be a time to reflect. We're in too deep right now."