Maria Sharapova: 'Kim Clijsters will be tough'

Maria Sharapova has admitted that she faces a tough match in the quarter-finals of the women's Olympic singles when she takes on Kim Clijsters later today.

The Russian third seed reached the last-eight thanks to a hard-fought victory over Sabine Lisicki on Wednesday, while Belgian Clijsters eased past 11th seed Ana Ivanovic.

"It's our first meeting on grass but she's such a tough competitor, such a great mover," said Sharapova. "She has so many great qualities as a tennis champion. It's always nice to play her, especially at this stage of an event like the Olympics."

The winner between Sharapova and Clijsters will play either Czech sixth seed Petra Kvitova or Maria Kirilenko of Russia in the semi-finals.