Seven-time women's tennis Grand Slam champion Serena Williams says she will miss two of the big tournaments this year because of a chronic left knee injury.

The 24-year-old American announced Wednesday that she will not play in either Wimbledon or the French Open. Williams reached the third round of the Australian Open in her only appearance on the court so far this year. Williams says she hopes to play in the U.S. Open, where she won her first major title in 1999.

The announcement came on the same day that her sister Venus Williams, the reigning Wimbledon champion, won her first match of 2006 at the Warsaw Open. She had played only two matches since a U.S. Open quarterfinal loss last year.

Some information for this report provided by AP and AFP.