Serena in stunning comeback to reach French Open third round

Power: Serena Williams plays a forehand return to Australia's Ashleigh Barty

Serena Williams battled back from a set and break down to defeat Australia's Ashleigh Barty 3-6, 6-3, 6-4 to reach the French Open third round on Thursday.

The three-time champion and former world number one, dressed again in her all-black catsuit, is playing her first Slam since winning the 2017 Australian Open while two months pregnant.

The 36-year-old, seeking a 24th Grand Slam title, will face Germany's Julia Goerges for a place in the last 16.

If she gets past the third round, Williams could face old rival Maria Sharapova for a place in the quarter-finals.

"It's just incredible," said Williams.

"I am so happy to be back here. I lost the first set and thought I must try harder, I must try harder and then Serena came out.

"I will be back tomorrow to play doubles with Venus. I don't mind playing singles and doubles -- I will fight my heart out."

Williams, playing in her first Slam since winning the 2017 Australian Open while two months pregnant, had cruised through her opening round match against Kristyna Pliskova in what was a record 317th win at the Slams.

But Thursday was a tougher proposition for the 36-year-old American who was playing just her sixth match of 2018.

Williams appeared once again in her striking, all-black catsuit.

However, her game failed to match her impressive outfit in the first set where she was broken in the sixth game by the Australian.

Barty wrapped it up when the American netted a weary-looking forehand, the 12th unforced error of the set for the 23-time major winner.

Williams hit just three winners in the opener while 22-year-old Barty could afford to bide her time, just two winners and four unforced errors.

She was a break down again after dropping serve in the opening game of the second set.

But just as the half-full crowd enjoying the late evening sunshine in Court Philippe Chatrier anticipated a quick kill, Williams came storming back, reeling off four straight games for 4-1.

A fifth ace of the contest won her the set.

A break in the third game of the decider proved crucial and Williams claimed victory on a second match point with a sweeping, running forehand.

Power: Serena Williams plays a forehand return to Australia's Ashleigh Barty