By Steve Ginsburg
WASHINGTON (Reuters) - Firing an ominous verbal volley to her Olympic rivals, Serena Williams says she is anxious to seize the one piece of serious hardware yet to adorn her trophy case: a gold medal in singles.
"It's getting closer and closer and I'm getting more excited," the 13-time grand slam winner said recently of the upcoming Olympics Games.
"I was in London yesterday and I saw a guy with a USA jacket on. I was like, 'Oh, man, this is really happening'. It's a great feeling, and I love that feeling.
"So I'm getting little butterflies in my stomach."
Williams has a pair of gold medals in doubles but has yet to break through in singles, losing a three-set, quarter-final heartbreaker to eventual champion Elena Dementieva in Beijing four years ago.
Although shut out from a grand slam title in 2011, U.S. Olympic coach Mary Joe Fernandez cautioned against counting out the 30-year-old American.
"We've seen in the past Serena turn it on without expecting it," she told Reuters in a telephone interview.
"She's come in unseeded at the Australian the one year (2007), out of shape, and work her way through the tournament and win it. We've seen it on numerous occasions.
"As she gets older, it means more to her. She's going to have this huge determination to win the gold in singles."
The Olympic tournament will be staged on grass at the All-England Club, site of the Wimbledon Championships. For Serena, it is a welcome change from Beijing's hardcourt event.
"The surface is great for her," said Fernandez, a two-time gold medalist in doubles. "She's won four Wimbledon titles with her great serve and how hard she hits the ball.
"The surface definitely enables her to play that much better."
In doubles, Serena will team with older sister Venus, her partner for Olympic titles in 2000 and 2008, and the singles champion at the 2000 Olympics in Sydney.
The sisters have never lost in doubles at the Olympics and Serena said coming into the London Games as defending champions is "kind of cool."
Serena said participating in the Olympics was "an experience I never thought I would have" growing up.
"As a tennis player you get to play grand slams, which you get to play every other week it seems," she said. "You don't think about the Olympics. It's just an added bonus.
"I played two Olympics, which is pretty awesome, and have two gold medals, which is even better."
(Editing by Julian Linden)