With the U.S. Open Tennis championship about to get underway in New York tomorrow, Mayor Michael Bloomberg (I) announced that he had received an endorsement from a tennis star and women's rights icon.

The incumbent mayor took to Twitter to say that former tennis star Billie Jean King had endorsed his reelection campaign.

King is famous for winning the 1973 "Battle of the Sexes" match against former Wimbledon champion Bobby Riggs and being one of the first female athletes to publicly declare her homosexuality.

He tweeted on Monday:

Proud to announce the endorsement of tennis legend and social activist Billie Jean King http://bit.ly/FG0gc #NYC #usopen

The U.S. Open, contested at Arthur Ashe Stadium in Queens, N.Y. is one of four high-profile "Grand Slam" tennis tournaments played during the season.

Bloomberg, whom the City Council allowed to run for a third-term against standing term limits, faces City Comptroller Billy Thompson (D) in the general election this November.