World No.1 Serena Williams stayed on course for the first calendar Grand Slam since 1988, advancing to the US Open semi-finals on Tuesday by defeating older sister Venus Williams 6-2 1-6 6-3.
Three-time defending champion Serena reached a Thursday semi-final against Italy’s 43rd-ranked Roberta Vinci, who eliminated France’s 40th-ranked Kristina Mladenovic 6-3 5-7 6-4.
Serena, who holds all four major trophies, moved to 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.
Playing at a high level throughout, the sisters staged a classic at Arthur Ashe Stadium, which was jam-packed with fans and celebrities, including US Presidential hopeful Donald Trump and TV mogul Oprah Winfrey.
“This is a big moment for Venus and I,” Serena said. “Very competitive. We were just trying to give each other a great match.”
Serena fired 35 winners with 22 unforced errors with 12 aces, the last coming on match point. Venus had 24 winners, 15 unforced errors and eight aces.
Three-time defending champion Serena, the younger sister by two years at 33, improved to 53-2 on the season and took a 16-11 edge in the sibling rivalry, including an 9-5 advantage in Grand Slam meetings and a 3-2 lead in US Open results.
Venus, seeded 23rd, sought her third US Open crown after 2000 and 2001 to add to a Slam trophy haul that also includes five Wimbledon titles, the most recent in 2008.
“She’s the toughest player I’ve ever played in my life and the best person I know,” Serena said of Venus.
“It’s going against your best friend and the best competitor in women’s tennis.
“When I’m playing her I don’t think of her as my sister. When you’re in the moment you don’t really think about it. For us it’s a really great honour.”
Serena is 4-0 in her career against Vinci, 32, who reached her first Grand Slam semi-final in her 44th Slam start.
“Amazing moment for me. It’s unbelievable,” Vinci said. “First semi-final in my career. I’m so happy, I don’t have words to say.”
Italian veteran Vinci reached her first Grand Slam semi-final at the age of 32.
The world No.43 saw off her 22-year-old opponent, who had never been beyond the third round at a major before this tournament, and struggled with cramping on a steamy afternoon in New York.
Mladenovic rallied from a break down in the second set to force a decider, but had trainers rubbing ice on her legs during changeovers.
At 3-3 in the final set, the two played a 15-minute game with 10 deuces. Mladenovic had six game points she failed to convert.
After her service was broken, the 40th-ranked Frenchwoman asked for a medical timeout to receive more treatment for cramping.
Vinci protested to the chair umpire as Mladenovic had her left thigh wrapped and it is against the rules to request treatment for an existing injury, but the world No.40 claimed it was a different problem.
It wouldn’t make a difference. Mladenovic repeatedly bent over in discomfort between points, and Vinci won her last two service games to clinch victory after two-and-half hours.