Serena Williams and Venus Williams face off for the first time in over three years on Saturday after booking a semi-final clash at the Family Circle Cup in Charleston.
The American superstar sisters have not played each other on tour since Serena beat Venus in the final of the season-ending WTA Championships in 2009.
But after both won two matches in a day on Friday, as the tournament got back on track following a rain-affected Thursday, they are set to resume their friendly rivalry.
Serena, the younger sister, leads their career series 13-10.
She saw off American qualifier Mallory Burdette 6-4 6-2 before knocking out Czech sixth seed Lucie Safarova 6-4 6-1 to make the all-Williams clash happen.
Venus had already clinched her place in the final four, at the expense of two fellow Americans, first knocking out Varvara Lepchenko 6-2 4-6 6-2 and then earning a 6-4 6-4 victory over Madison Keys in the quarter-finals.
Serena is defending her title this week and, as world number one, heads into the semi-final against 24th-ranked Venus as favourite.
“It was really motivating to see Venus win today [Friday]. I figured if she can win two matches, I have no excuse not to win my two matches,” Serena Williams said, according to the WTA website.
Now 31-year-old Serena is relishing the battle against her 32-year-old sister.
“Venus is the toughest opponent I’ve ever played. I think she’s beaten me the most out of any player. I know her game and she knows my game,” Serena said.
“I think it’ll be a great match tomorrow [Saturday].”
Jelena Jankovic ended the run of qualifier Eugenie Bouchard, with the Serbian posting a 6-2 6-1 victory over her Canadian opponent.