DUBAI, UNITED ARAB EMIRATES - FEBRUARY 20: Serena Williams of USA attends a press conference as she withdraws from her evening match against Marion Bartoli of France during day three of the WTA Dubai Duty Free Tennis Championship on February 20, 2013 in Dubai, United Arab Emirates. (Photo by Julian Finney/Getty Images)

DUBAI, United Arab Emirates – Serena Williams has withdrawn from the Dubai Championships because of a lower back injury.

Williams took over the No. 1 ranking last week in Qatar, the sixth time in her career she has been the top-ranked player in the world.

Last year, she won the Wimbledon and U.S. Open titles, as well as the Olympic gold medal.

Second-ranked Victoria Azarenka, who beat Williams in the final in Qatar last week, also withdrew from the tournament in Dubai, citing a bone bruise in her right foot. – Sapa-AP