PARIS, May 28 (Reuters) - Coco Gauff overcame a hard-fought 6-3, 6-2 battle over Egypt's Mayar Sherif on Thursday to advance to the third round of the French Open tennis tournament.

The American, who achieved her 80th career victory in the main draw of the four Grand Slam tournaments, did not reach her best level and faced fierce resistance from the Egyptian player who came through the qualifiers in the first set.

"It was a physically tough match," said Gauff, the defending champion. "I was really tested today. I needed a lot of strength today."

"I will focus on getting my rhythm back because I was unable to do that today."

Mayar tried to confuse her opponent with high shots at the start of the match, but Gove quickly went up 3-0.

Her bright start seemed to fade when Mayar, who was trying to become the first Egyptian to reach the third round of a major tournament in the professional era, broke back.

Mayar had several opportunities to level the score in the sixth game, which lasted for more than 13 minutes, but Gauff regained her composure in time to protect her lead and sealed the set with a powerful serve after one hour and three minutes.

The two players traded breaks of serve at the start of the second set, and Mayar raised her hands in the air in celebration when she succeeded in breaking her opponent's serve to level the score at 2-2.

But she couldn't keep up the chase, and Gauff broke serve again, sealing the win on her first opportunity after an hour and 50 minutes.

In her next match, she will face either Britain's Katie Boulter or Austria's Anastasia Potapova.