NEW YORK - World number one Serena Williams, seeking her 17th Grand Slam title, leads a charge of 31-year-olds into Friday's US Open semi-finals, all of them hoping to become the event's oldest women's champion.
Defending champion Williams faces Chinese fifth seed Li Na while Italy's 83rd-ranked Flavia Pennetta will meet second seed Victoria azarenka of Belarus at Arthur Ashe Stadium to determine the finalists for Sunday's title showdown.
Williams, Li and Pennetta are all 31 and would surpass the current age mark of Australian Margaret Court, who was 55 days beyond her 31st birthday when she captured the 1973 crown.
Azarenka, the self-proclaimed "baby" of the group at 24, has won the past two Australian Open titles but lost to Williams in last year's US Open final.
Williams, the reigning French Open champion, is 8-1 all-time against Li and has dropped only 13 games in five matches without losing a set on the New York hardcourts.
Li, the 2011 French Open champion, has played Williams tough, forcing a tie-breaker or 7-5 set in every defeat, including their most recent match, a 7-5, 7-5 triumph for the American in a semi-final last month at Cincinnati.
"She's a great challenge," Williams said. "She moves really well. She does everything well.
"She has been playing really close. Who knows? Maybe the next time we play she might want to go from close to a win, so I have to be ready for that."
Li knows dethroning a four-time US Open champion will be a heavy challenge, but she has been aggressive and formidable herself in the Flushing Meadows fortnight.
"It's a tough, tough opponent," Li said. "But it's a good challenge to play against her, because I think we always have a tough match, even in Cincy.
"Yeah, I still have a chance."