US fourth seed Serena Williams advanced to the US Open semi-finals for the fourth time in five years on Wednesday by defeating Serbian 12th seed Ana Ivanovic 6-1 6-3 in 58 minutes.

Three-time champion Williams, a 14-time grand slam winner who lost to Samantha Stosur in last year's final, will next play on Friday against Italian 10th seed Sara Errani for a berth in Saturday's championship match.

"It's going to be a good matchup. She is such a fighter. She's so strong and quick," Williams said. "I'm just so happy to be in the semis. It's so cool."

Williams has only dropped 16 games through five matches while blasting a tournament-best 41 aces, including 12 against outmatched Ivanovic, a former World No.1 who won a grand slam title at the 2008 French Open.

"I came out really strong," Williams said. "Playing someone like Ana, the former No.1, I knew I had to come out strong and play some amazing tennis."

In other action Maria Sharapova advanced to the semi-finals for the first time since winning the title in 2006, rallying to defeat French 11th seed Marion Bartoli 3-6 6-3 6-4.

The Russian third seed, who improved to 12-0 in three-set matches this year, reached a Friday semi-final against World No.1 Victoria Azarenka, who beat Sharapova in the Australian Open final, for a berth in the championship match.

Azarenka, the top seed from Belarus who ousted Australian defending champion Samantha Stosur on Tuesday, leads the all-time rivalry with Sharapova 5-4, including a 6-3 6-0 victory in January's Melbourne final.

Errani, the 10th seed, became the first Italian woman in the Open era to reach the US Open semi-finals with a 6-2 6-4 victory over 20th-seeded compatriot, doubles partner and best friend Roberta Vinci.

"It's always hard to play against a friend and it was strange seeing her on the other side of the net," said Errani.