Serena Williams began her quest for a 24th Grand Slam title with a tough win over fellow American Kristie Ahn in the French Open first round.

Williams, who turned 39 on Saturday, overcame a poor start to win 7-6 (7-3) 6-0 in Paris.

The sixth seed began to play with more belief and clarity as she swept Ahn aside in a one-sided second set, from the 74th minute.

Williams will play Bulgaria’s Tsvetana Pironkova in the second round.

Pironkova, 33, was handed a wildcard by Roland Garros after a memorable run to the US Open quarter-finals – where she lost to Williams – in her first tournament since 2017 after giving birth.