World number one Serena Williams has admitted that she had to overcome first-round nerves to beat Alize Lim in the French Open this afternoon.

Williams eased into the second round with a seemingly comfortable 6-2 6-1 victory, although her total of 36 unforced errors betray the fact that she was not at her best.

The defending champion needed five match points to eventually dispatch of Lim, but having reached the second round she revealed that she is not putting as much pressure on herself as she did last year.

"A lot of the games went to 30-30 or so. So I think the games were actually pretty close. It was interesting. I was a little nervous, like I always am in my first round. It's always hard for me to shake those nerves and go from there," Williams told reporters.

"I was in really top form last year on the clay, or at least I thought I was. This year I'm just going day by day. I do have to say this year I don't feel as much pressure on myself as I did last year."

Williams lost in the first round of this competition in 2012 but bounced back last year to win the title for the first time in 11 years.