An ailing Serena Williams stayed on course for a 20th grand slam singles title as she came back from the brink to reach the final of the French Open with a 4-6 6-3 6-0 win against Swiss power hitter Timea Bacsinszky yesterday.

The American, who looked unwell throughout the match, putting iced towels around her neck and against her forehead at changeovers, fell a set and a break down as the 23rd-seeded Bacsinszky peppered the court with backhand winners.

But Williams, who won Roland Garros in 2002 and 2013, dug deep to break back and Bacsinszky cracked, losing 10 games in a row.

Williams closed it out when Bacsinszky sent a backhand long and the world number one will now face Czech 13th seed Lucie Safarova tomorrow.

“I have tried everything. I thought if I lose I must fight. I have tried and tried, I don’t know where I found the energy,” Williams told a courtside interviewer in French before a coughing fit ended the conversation.

Meanwhile, Safarova became the first Czech woman in 34 years to reach the French Open final after she fought back to topple 2008 champion Ana Ivanovic 7-5 7-5.

Just when it looked as if her title aspirations were floundering, the 13th seed shook off her jitters and unleashed her A Game to pummel Ivanovic into submission.

“It’s a dream come true, I still cannot believe it. The happiness is unreal,” said Safarova, who will be aiming to become the first Czech to lift the Suzanne Lenglen trophy since Hana Mandlikova in 1981.