Serena sets up Halep showdown at Indian Wells

"It'll be a really good match I think for both of us to kind of see where we want to be at this point in the year," top seed Williams yesterday told reporters of the showdown against the Romanian in California.

"I really like her game. I like how she's aggressive. She's a fighter. I definitely have to be ready."

The American world number one, a 21-time grand slam champion, is looking for her first title at Indian Wells since 2001.

Halep moved a step closer to repeating last year's triumph after her opponent Barbora Strycova retired with the world number five leading 6-3 1-0.

The Romanian has only defeated Williams once in her career, a 6-0 6-2 thrashing in the group stages of the 2014 WTA Finals that the American avenged in an equally as one-sided final.

The pair were due to meet in the semi-final of this tournament a year ago but Williams was forced to withdraw ahead of the contest through a knee injury.

"I know that it's gonna be tough to win, but still, I have my chance," Halep said.

"I feel that I have the game to play against her. We will see tomorrow. She's number one in the world."

In earlier women's action, Polish third seed Agnieska Radwanska beat Serbia's Jelena Jankovic 6-3 6-3 to reach the quarter-finals, where she will face world number nine Petra Kvitova.

Radwanska, who was a runner-up in the event two years ago, broke last year's losing finalist six times in an error-strewn contest in which both players struggled on serve.

Two-time Wimbledon champion Kvitova ended the fairytale run of American qualifier Nicole Gibbs, rallying for a 4-6 6-3 6-4 win to book her spot in the quarters.

Kvitova imposed her left-handed power to overcome Gibbs, swatting 27 winners to 11 for the American and claiming 18-of-25 points at net to prevail.

"It's always tough coming back after losing the first (set)," said the Czech, who has needed three sets in each of her three victories. "We both played really well in the third set so I was happy to get the win."

Italian ninth seed Roberta Vinci retired from her match against unseeded Magdalena Rybarikova while trailing 2-6 0-2.

Victoria Azarenka, Timea Bacsinszky and Karolina Pliskova were also winners.