PARIS, France - Top seed Simona Halep not only surged into her third French Open final, but also won a battle for World No.1 over 2016 champion Garbiñe Muguruza, 6-1, 6-4, booking a clash with 2017 US Open winner Sloane Stephens for her first major title.

"I'm really happy that I could beat a player like Muguruza," Halep said after the match. "She's a great opponent, a great player, and it's always tough against her.

"I think I played very well, and even if I repeat it, I played the best match here. So every day I play better and that makes me happy."

Halep had to beat the Spaniard to retain her spot atop the WTA rankings, and it never going to be easy for the Romanian, who had lost three of her four previous meetings with Muguruza - most recently at the Western & Southern Open final last summer.

Her one win, however, came on clay at the Porsche Tennis Grand Prix back in 2015, and Halep appeared lightyears more comfortable on the terre battue on Thursday, racing out to a 5-0 lead to kick off the Court Philippe-Chatrier clash.

"Sometimes it's working well, sometimes not. But if you finish the match in a good way, doesn't matter that much. Today was just I felt good on court, I felt positive, and I started to play very well since the beginning."

Muguruza eventually got on the board and started to settle into the second set, breaking serve and getting to within two games of a decider at 4-2. Halep nonetheless rallied and won a thrilling ninth game, one that saw her save three break points with some fearless hitting.

"I think it was the most important game of the match. The fact that I could win that long game, I won the next one easily, so it was a little bit of mental part in the last game. I just didn't give up. I was a little bit upset of what I have played those points. I had two double faults, so it was a bit tough.

"But I stayed calm. I stayed focused, dnd I didn't give up, which is the most important thing in my game. Then I was very confident that I can finish."

With the momentum back on her side, the Romanian broke to love to secure victory in 92 minutes and return to her second straight final in Paris.

Halep looked supremely confident off the ground - even against Muguruza's obvious power - and struck 16 winners to 24 unforced errors.

For Muguruza, the two-time major will rue her missed break point opportunities, converting just two of eight compared to Halep's six of 10.

An American awaits in the final, as Sloane Stephens beat Madison Keys in a rematch of the US Open final. Halep has won her last four matches against Stephens - two last summer at the Citi Open and Western & Southern Open. The pair played at the French Open back in 2014, where Halep won en route to her first Grand Slam final.

"I know that she's strong opponent. She's hitting the ball. I will be similar to today. I will play my game against her, as I did last year. It's clay. It's different. It's different match, different year. So I expect nothing. I just want to go there and try to keep my tactic and keep my positive things every second.

"I will focus on myself, like I did every match here. And I will try just to be calm during the match and try everything I can. It's a nice opportunity, a big challenge, so I have just to feel happy after the match that I gave everything."