Unknown illness sidelines Venus

World number six Venus Williams has won six Grand Slams

Venus Williams has pulled out of next week's Family Circle Cup in Charleston - increasing doubts about her fitness for next month's French Open.

It is the second consecutive event Williams will miss for unspecified medical reasons.

"I've been having some issues that I need to resolve," said the 27-year-old four-time Wimbledon champion.

"I am working on that at the moment and I am hoping to be back playing as soon as possible."

The 27-year-old intends to play in the Italian Open, which starts on 12 May - two weeks ahead of the French Open.

"I look forward to returning to competitive play in Rome," she added.