Serena eyes history

World number one Serena Williams stayed on course for the first calendar Grand Slam since 1988, advancing to the US Open semifinals Tuesday by defeating older sister Venus Williams 6-2, 1-6, 6-3.

Three-time defending champion Serena will now face Italy's 43rd ranked Roberta Vinci on Thursday's semifinal.

Serena, who holds all four major trophies, moved two wins from completing the first calendar Grand Slam since Steffi Graf 27 years ago and matching Graf's career Open Era record of 22 singles titles, two shy of Australian Margaret Court's all-time mark.

"This is a big moment for Venus and I. We were just trying to give each other a great match. She's the toughest player I've ever played in my life and the best person I know," Serena said of Venus.

Serena and her family want winning the calendar Grand Slam to be a huge achievement if Serena does it, but not so big a deal if she fails.

"It is important to me, but at the same time, it is what it is," Serena said of her quest to complete the calendar Slam. "I'll do what I can."

Venus said that while Serena has been downplaying the calendar Slam, she and the Williams family see it as potentially the crowning achievement on their legend of coming from a poor neighbourhood near Los Angeles to global tennis stardom.

"That would be huge, not just for me, but for my family just for what it represents and how hard we have worked and where we come from, so it would be a moment for our family," Venus said.

"But at the same time, if it doesn't happen it's not going to make or break you. We don't have anything to prove."

On Wednesday, Italy's 26th-ranked Flavia Pennetta shocked two-time Wimbledon champion and Czech fifth seed Petra Kvitova 4-6, 6-4, 6-2 to reach her second US Open semifinal.

Pennetta next will play against the winner of the match between two-time Australian Open champion Victoria Azarenka, the 20th seed from Belarus, and Romanian second seed Simona Halep for a berth in Saturday's final.

Pennetta, 3-1 all-time against Haelp and 2-2 against Azarenka, matched her best Grand Slam run from the 2013 US Open semifinals, where she lost to Azarenka.

"I'm really happy right now," Pennetta said. "I was just trying to fight every ball, running and push everything I can.

"I didn't think to get through this match. In the second set I was playing and playing -- it was unbelievable."

In the men's quarterfinals, Novak Djokovic defeated Feliciano Lopez 6-1, 3-6, 6-3, 7-6 (7/2) to reach the US Open semifinals, a 21st last-four spot in his last 22 Grand Slams.

The top seed and 2011 champion, playing in his 26th consecutive quarterfinal at the majors, claimed his 55th match win in New York.

Djokovic will take a staggering 13-0 career record over defending champion Marin Cilic into their Friday semifinal.

Cilic reached the semifinals with a 6-4, 6-4, 3-6, 6-7 (3/7), 6-4 win over France's Jo-Wilfried Tsonga.

Over a four-hour battle on Arthur Ashe Stadium, 26-year-old Cilic claimed a fifth win in six matches against Tsonga, firing 29 aces and 63 winners.

But the 30-year-old Tsonga made him work in 35-degree (95 F) heat, saving four match points before the champion went through.