Flavia Pennetta continued her remarkable US Open by defeating fellow Italian Roberta Vinci to reach her first grand slam singles semi-final.

The 31-year-old had made the quarter-finals in New York three times before but was well off the radar before the tournament began. Initially, Pennetta was not even ranked highly enough to get into the main draw but crept in after a withdrawal.

The world number 83 is a former top-10 player but missed this tournament last year and the following six months because of a wrist injury.

She struggled when she returned to the tour, winning just three matches in her first seven tournaments and dropped out of the top 100. But a run to the semi-finals in Strasbourg in May as a qualifier showed her form was coming back and she reached the fourth round at Wimbledon.

Pennetta had reached the last eight without dropping a set, beating fourth seed Sara Errani in the second round, former champion Svetlana Kuznetsova in round three and in-form Simona Halep in the last 16.

She was always the dominant player again today, her extra power giving her the edge over 10th seed Vinci, and she eased to a 6-4 6-1 victory.

Vinci had been the winner on Tuesday when the pair met in doubles but, after pulling back from 2-4 to 4-4, she lost her serve again and the set.

The second set was much more one-sided.