Elina Svitolina secured her first ever win over Ana Ivanovic to reach the last 16 of the French Open, while Serena Williams had to work hard against a tenacious Kristina Mladenovic.

After seven successive defeats, including a pair at Roland Garros, Svitolina finally got the better of 2008 champion Ivanovic 6-4 6-4 in the third round.

Williams, meanwhile, scrapped with Mladenovic but the world number one came away with a 6-4 7-6 (12-10) victory following more than two hours off court due to a rain delay.

The American and Svitolina will now go head to head for a place in the quarter-finals.

SVITOLINA PRAISES HENIN IMPACT

Former world number one Justine Henin joined Svitolina's coaching team this year, and the Ukrainian believes the advice on offer from the Belgian has been integral to her displays at Roland Garros.

"I think her experience is when she was playing on court and she understands what I feel, and that's the main key, I think," said Svitolina.

"Because for some coaches who didn't play on such a high level, it's tough, I think. It's just different."

WILLIAMS PASSES FRENCH TEST

It may have been a straight-sets win, but Williams' victory over Mladenovic was far from routine.

The defending champion produced 31 unforced errors and converted just one of 12 break points that came her way.

After a lengthy delay due to a thunderstorm, Williams had to stave off a set point that would have forced a decider before converting match point at the fifth attempt.

BERTENS CLAIMS WIN AFTER MARATHON DECIDER

Kiki Bertens awaits Madison Keys in the fourth round, but she required almost three hours to see off 29th seed Daria Kasatkina.

Bertens had five opportunities to take the third set 6-4, but Kasatkina showed great resilience to remain in the contest.

Neither player could make their serve stick until the Dutchwoman held in game 17 before securing a break for a 6-2 3-6 10-8 triumph.

KEYS UNLOCKS FOURTH ROUND

Keys booked her place in the last 16 of the French Open for the first time by defeating Monica Puig 7-6 (7-3) 6-3.

The pair met at Roland Garros in the second round of the 2013 edition of the competition, with the Puerto Rican coming out on top in straight sets.

Keys was beaten by Williams in the Internazionali d'Italia final this month and is pleased to be maintaining that form.

"I definitely wanted to keep doing everything that I was really doing well in Rome. Today I don't think I played extremely well all of the time, but being able to figure it out, I think that's where having a lot of matches really helped me," she said.