Washington, Dec 25 - Swiss tennis ace Roger Federer has reportedly said on Twitter that he and his wife Mirka are expecting another child next year.

The 17-time Grand Slam winner, who has spent more weeks at No. 1 than anyone else in the history of the ATP rankings, is the father of twin daughters Charlene and Myla, who were born in July 2009.

According to the Huffington Post, Federer tweeted that he and Mirka are happy to share the news that their daughters would be 'big sisters' in 2014.

Federer's agent confirmed to the media that the tweet is legitimate, the report added. (ANI)