Williams sisters battle it out at the US Open

THEY may be the best of friends but the Williams sisters will be doing it for themselves when they clash in the quarter-finals of the US Open.

World No. 1 Serena kept her 2015 grand slam dream alive when she beat Madison Keys 6-3 6-3 to set up a final eight showdown against older sister Venus who downed Estonian qualifier Anna Kontaveit 6-2 6-1.

Serena leads Venus (pictured) 15-11 in the head-to-head battle, although Venus will no doubt draw on her win in last year's Canadian Masters.

"She's beaten me so many times," Serena said. "So yeah, she's a player that knows how to win, knows how to beat me, knows my weaknesses better than anyone. She's doing well, and she wants to win this. So do I. It's not going to be easy."

In the men's quarters, top seed Novak Djokovic will take on Spain's Feliciano Lopez, while defending champ Marin Cilic will meet Jo-Wilfried Tsonga.