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.