NEW YORK - The Williams Family show took centre stage at the U.S. Open with Serena and Venus both cruising to straight set wins on Sunday to set up a monster quarter-final between the tennis siblings. Whenever the Williams sisters clash on court it is a major tennis event but with older sister Venus, a twice U.S. Open winner, standing in the way of defending champion Serena's quest for a rare calendar-year grand slam their meeting on Tuesday has been elevated to a must-see sporting viewing.

While the National Tennis Center was abuzz over another Williams grand slam showdown, world number one Novak Djokovic was hard at work taming Spaniard Roberto Bautista Agut 6-3 4-6 6-4 6-3 to reach his 26th consecutive grand slam quarter-final. Only Roger Federer (36) and Jimmy Connors (27) have registered more consecutive grand slam quarter-final appearances than Djokovic since the slams began including professionals in 1968.

With Serena bidding to become just the fourth woman to win all four grand slams in the same year, the U.S. Open hype machine that already had been in top gear is now set to crank into overdrive. The Williams sisters have met 26 times over their careers with Serena coming out on top 15-11 but meeting number 27 will have more than the usual family bragging rights riding on the outcome.

"Obviously getting to a Grand Slam semifinal is the next step toward the final. Pretty clear what's up for grabs here," said Venus. "I think people love to see history being made. "No one is out to be a spoiler, but at the same time, you're focused on winning your match even though the circumstances are really much different than you. "You still have to prepare, still have to play well. "Even though you're playing your sister you have to be prepared and focus. The preparation doesn't change."

The 35-year-old Venus, seeded 23rd, overpowered 19-year-old qualifier Estonian Anett Kontaveit 6-2 6-1 in a ruthless fourth-round display that took just 50 minutes. Serena followed her sister onto Arthur Ashe Stadium court and was no less efficient, routing fellow American Madison Keys 6-3 6-3 in 68 minutes. "She's playing great," 33-year-old Serena said about seven-times grand slam winner Venus, who is two years her elder. "I have to really be ready for that. "At least one of us, a Williams, will be in the semis."

Two-time runner-up Victoria Azarenka reached her fourth US Open quarter-final on Monday with a 6-3, 6-4 win over Varvara Lepchenko of the United States. Former world number one Azarenka, the 20th seed, will face either Romanian second seed Simona Halep or Sabine Lisicki, the 24th-seeded German, for a place in the semi-finals.

The Belarusian, whose season has been stalled by a left thigh strain, appeared on Arthur Ashe Stadium with both biceps tightly strapped. "It's a little embarrassing. I have blisters from my shirts rubbing against my arms so I needed the bandages," said Azarenka, the runner-up to Serena Williams in 2012 and 2013. "It looks weird but I did what I have to do." Defending champion Marin Cilic kicked off centre court action on another sunny day at Flushing Meadows and was the first man through to the last eight, taking down determined Frenchman Jeremy Chardy 6-3 2-6 7-6(2) 6-1 to extend his U.S. Open win streak to 11 matches.

Coming off a punishing five-setter with Mikhail Kukushkin in a third-round match that lasted four hours, Cilic took a while to find his power game but was unstoppable once he did, the ninth seeded Croat blasting 23 aces past 27th seed Chardy, who had no answer. "Key today was finding my rhythm on the serve, especially towards the end of the third set," said Cilic.

"I played really good in the fourth set, really great tennis, so I'm happy about it."

After splitting the opening two sets, Cilic's power began to show through, particularly in the third set tiebreak when he used his big serve to full advantage firing four aces and going up 6-1 before closing out 7-2. Four Frenchmen made the round of 16, a U.S. Open record, and at least one advanced to the quarter-finals, with Jo-Wilfried Tsonga beating countryman Benoit Paire 6-4 6-3 6-4.

Fabio Fognini, who toppled Rafa Nadal in an epic five-setter that ended early Saturday morning, had nothing left in his tank for his fourth-round clash with Feliciano Lopez, the 18th seeded Spaniard easing to a 6-3 7-6(5) 6-1 win.