Sisters Venus and Serena Williams will again go against each other for the U.S. Open quarterfinals on Tuesday night.

ESPN said this came after Serena bested Madison Keys in a 6-3, 6-3 victory while Venus outclassed Estonia's Anett Kontaveit 6-2, 6-1 during a fourth-round match.

For them to be able to move to the next step of the competition, the sisters will have to fight against each other. If Serena wins, she would be two matches away from winning a Grand Slam, as per ESPN.

But the younger Williams commended her sister for her recent victory.

"She's playing great. I barely had time to get ready for my match because she won so fast. I have to be ready for that. At least a Williams will be in the semis, so that's good," Serena said in the ESPN report.

Asked about her potential Grand Slam victory, Serena said she is not pressured by expectations.

"I don't feel any pressure. I wanted that Serena Slam. Winning four in a row at Wimbledon was amazing. Now I have a chance to go for it here, five in a row," she added.

With her victory against Keys, Serena told BBC that she knew it was a difficult fight but came prepared for it.

"I served much better today. I'm so proud I was able to serve better. Obviously I had to -- I knew I wouldn't have too many chances to break," she added.

As for Venus, she said she is focused on what she can do on the court despite what it can potentially do to her sister's ultimate Slam goal.

"I don't think anyone wants to be a spoiler. I think people love to see history being made. No one is out to be a spoiler, but at the same time, you are focused on winning your match, even though the circumstances are really much different," Venus said in the New York Times report.

The Los Angeles Times added that their next match will be their "26th meeting" with Serena winning twice in the three times they played since 2013. This was partly attributed to her strong physical health compared to Venus' who suffered an illness that sacrificed her stamina.

Venus ultimately said that at the end of the day, they are sisters and are proud of each other.

"It's awesome. I'm proud of her. She's proud of me," she added.

Meanwhile, Serena said that she will be taking on a really tough opponent.

"I'm playing the best player in the tournament. She knows how to play, how to win. She knows all my weaknesses. We have proven you can be enemies on the court and friends after," the younger Williams told the Los Angeles Times.