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Serena Williams is just two wins away from making history -- well, making more history.

In what turned into a fantastic match, Williams beat Simona Halep, 6-2, 4-6, 6-3 on Wednesday night to advance to the semifinals of the U.S. Open.

"I knew that I could play a lot better," Williams said after the match. "I felt like I kind of lost my rhythm a little bit in the second set, and also Simone started playing really well. ... I knew if I wanted to win this I had to step it up in the third set."

The 34-year-old is seeking her 23rd career major title, which would set a new women's Open era record. She's currently tied with Steffi Graf atop the list. A win at this year's U.S. Open would be Williams' seventh, which would break a tie with Chris Evert for the most ever.

Williams has already made history at the U.S. Open, having picked up her 308th Grand Slam singles match win on Monday. That put her ahead of Roger Federer for the most all-time, male or female.

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Serena Williams advanced to the U.S. Open semifinals. USATSI

Win No. 309 wasn't as easy as her previous wins at this year's Open, as Williams dropped a set for the first time in the tournament. It looked like it was going to be business as usual after the 6-2 first set, but Halep showed tremendous grit and took the second set from Williams, 6-4.

Williams finally broke Halep to go up 3-1 in the final set, and she never relinquished control.

Despite battling a shoulder injury, Serena Williams took home her seventh Wimbledon singles title in July to tie Graf's career Grand Slam record. She's coming off a third-round loss at the 2016 Rio Olympics, and entered the U.S. Open having played only three matches since Wimbledon.

Williams has been ranked No. 1 in the world for 186 straight weeks, tied with Graf for the most ever. In order to maintain her streak and break Graf's record she'll have to at least make the U.S. Open final -- if her opponent in the final is Angelique Kerber, Williams will have to win the title to stay No. 1.

In Thursday's semifinal Williams will face Karolina Pliskova, who defeated her sister Venus earlier in the tournament.

Should she advance, she'll face the winner of Kerber and Caroline Wozniacki in Saturday's final.