US Open: Grand Slam-seeking Serena reaches quarters against Venus

Serena Williams moved within three wins of achieving the fourth women's calendar-year Grand Slam by routing fellow American Madison Keys on Sunday and setting up a US Open quarter-final clash with sister Venus.

Williams beat the 20-year-old Keys 6-3 6-3 in 68 minutes to book a 27th professional career showdown with her older sister, who advanced with a 6-2 6-1 fourth-round victory over Anett Kontaveit, 19, of Estonia.

Three-time defending champion Serena holds a 15-11 advantage in the sisterly head-to-head series against Venus, splitting their four previous clashes at the US Open.

"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."

Serena, winner of 21 grand slam singles titles including this year's Australian Open, French Open and Wimbledon championships, would match Maureen Connolly (1953), Margaret Court (1970) and Steffi Graf (1988) should she win her seventh US Open crown.