Maria Sharapova edges Nadia Petrova in New York

Maria Sharapova was pushed all the way by Nadia Petrova but battled back to make the last eight at Flushing Meadows tonight.

The third seed got off to a dominant start and took the first set against her Russian rival 6-1.

Petrova improved dramatically in the second and leveled the match at a set apiece.

Sharapova continued to struggle early in the third set and trailed 2-0 before rain delayed the match for over an hour.

When the players returned Sharapova regained her composure and broke Petrova's serve twice to win the deciding set 6-4.

Sharapova will now play Marion Bartoli in the quarter-finals after she overcame Petra Kvitova with a superb comeback to knock out the fifth seed.