Top seed Maria Sharapova dallied a little longer on court at the US Open on Friday before reaching the fourth round at Flushing Meadows for the first time.

The Russian beat German Julia Schruff 6-2 6-4 in match lasting over an hour on Arthur Ashe Court. She had lost only three games in the first two rounds combined and can expect an even tougher test in the last 16 against fast-rising Indian Sania Mirza.

Schruff, ranked 87, won only one point in the first three games but put up a fight in the second set, recovering from a break down to level at 4-4 before slipping to defeat.

Sharapova's preparations for the tournament were limited by a pectoral muscle injury and she said: "I felt pretty good. I haven't had that many matches coming to the Open so it's good to get three matches in before the tough ones come.

"So far so good. When the tougher matches come I'm going to put more power into my shots."

Mirza became the first Indian woman to reach the fourth round of a Grand Slam when she knocked out France's Marion Bartoli 7-6 6-4.

Mirza has a huge following among the one-billion-strong population of India and her match with Sharapova, herself a global tennis phenomenon, promises to be one of the highlights of the tournament.

"I just came here thinking I wanted to win one round and won three," said Mirza who is ranked 42. "I'm very happy about it."

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