World number one Serena Williams has admitted that she was feeling nervous during her first-round victory against Alize Lim at the French Open.

The defending champion sealed her progress at Roland Garros on Sunday with a convincing 6-2 6-1 triumph over the French world number 138.

However, Williams insists that she was far from complacent during the encounter.

"The game were actually pretty close. A lot went to 30-all. It was interesting," the American told reporters. "I was a little nervous as I always am in my first round. It's always hard for me to shake those nerves and go from there."

Williams will now face Spaniard Garbine Muguruza for a place in the third round of the tournament.