World number one Williams was winner of the past two titles at Flushing Meadows and five overall.

Wozniacki, dramatically qualified after her opponent, China’s Peng Shuai succumbed to heat related illness. She was leading 7-6 (7/1) 4-3 .

The American superstar needed exactly one hour to subdue Makarova, who was playing in her first Grand Slam semi-final after coming up empty in four prior quarter-final appearances.

Although she’ll be trying to join Chris Evert and Martina Navratilova on 18 career major titles, Williams hadn’t made it past the fourth round at any of the year’s three other Grand Slams.

“Oh my God, it feels so good,” said Williams, who sank almost to her knees screaming “Yes!” when Makarova pushed a last ball wide. “I’m so happy, you have no idea.”

Williams played three straight tournaments in the build-up to the Open, winning titles in Stanford and Cincinnati and reaching the semi-finals in Montreal.

Along the way she beat Wozniacki twice, in the quarter-finals at Montreal and semis in Cincy, both times needing three sets.

“It’s definitely given me a lot of confidence, playing all summer,” Williams said, adding that she was looking forward to playing her good friend Wozniacki — and perhaps improving her 8-1 career record over the Dane.

“She obviously wants to win and go for her first Grand Slam and I want to win and make a little history,” Williams said.