PARIS (AFP) - Defending champion Serena Williams needed five match points before downing battling French hope Kristina Mladenovic 6-4, 7-6 (12/10) to reach the last 16 at Roland Garros on Saturday.
The top-seeded American, chasing a fourth Paris title and record-equalling Open era 22nd Grand Slam crown, goes on to face Ukraine's 18th seed Elina Svitolina for a place in the quarter-finals.
But it was a tough afternoon for the 34-year-old Williams and her 26th-seeded opponent who needed to sit out a two and a half hour rain delay before the second set tie-break could commence.
Mladenovic even had a set point at 9/8 in the breaker but finally wilted on a fifth match point when she went wide with a forehand.
"She played really, really well and forced me to bring out my best tennis," said Williams, the 2002, 2013 and 2015 champion.
Williams saved three break points in the ninth game of the opening set against an aggressive Mladenovic, two with aces.
The American made the 23-year-old Frenchwoman pay in the next game, racing to three set points on her way to the pocketing the opener.
As thunder and lightning rocked Roland Garros, Mladenovic had to save three break points in the fourth game of the second set, two more in the sixth and another in the eighth.
The former junior champion held on until the tiebreak when torrential rain sent the players off Court Philippe Chatrier.