NEW YORK, NY, USA - 23-time Grand Slam champion Serena Williams kept up her solid play under the lights of Arthur Ashe Stadium, dismissing Carina Witthoeft, 6-2, 6-2, to reach the third round of the US Open, where she will face sister Venus.

"I wouldn't say it's exciting," Serena admitted of the upcoming match. "But it's definitely going to be a really tough match for me. Once again, it's early in the tournament. You know, it is what it is."

Playing just her second match in New York since marrying and giving birth to daughter Alexis Olympia Jr., Williams showed marked improvement from her return on Monday, striking 13 aces to knock Witthoeft out in 67 minutes.

Serena struck first to start the match, and even as Witthoeft broke right back, the American remained in control, reeling off the final three games of the opening set.

The former World No.1 survived a long seventh game to hold onto her break advantage, and promptly broke serve once more to secure her spot in the Round of 32.

"I think Patrick told me I served really well today. I agree. Even though I was broken, I feel like I was able to serve pretty well today. So that was pretty good."

In all, Williams hit twice as many winners as errors - 30 to 15, and converted five of six break point opportunities. Known for her big hitting game, Witthoeft could only mange 10 winners of her own and 15 unforced errors in two sets.

Up next for Serena is her elder sister, whom she'll face for the 30th time in their storied careers. The pair last played in Serena's first tournament back at the BNP Paribas Open in Indian Wells; their 2015 US Open encounter was a thrilling three-setter.

"I never root against her, no matter what. So I think that's the toughest part for me. When you always want someone to win, to have to beat them. I know the same thing is for her. When she beats me, she always roots for me as well. I think that's just the hardest part.

"The best part is we bring out the best in each other. I know when I play her, I have to play some of my best tennis. She does, too. It propels us to continue to play that for the tournament. It sets a tone for us. I feel like throughout our career, we have pushed each other to be the best that we can be, and be Venus and Serena Williams."