Serena and Venus Williams plan to play doubles at the 2016 Rio Games for a chance to win their fourth gold medal.

The sisters, accompanied by their mother Oracene Price, will play an exhibition match against each other Friday in Nigeria's largest city of Lagos.

They are excited about competing in Rio de Janeiro, even though the games are four years away.

"It's our main goal," Serena Williams said. "We were talking ... about how we can't wait to get to Rio. And obviously, bearing that we're both healthy, that's our goal to be there."

Venus and Serena teamed to win 13 Grand Slam doubles titles and won Olympic gold in doubles in 2000, 2008 and 2012. This year, the sisters beat Andrea Hlavackova and Lucie Hradecka of the Czech Republic 6-4, 6-4 at the London Games.

On Sunday, Serena beat top-ranked Victoria Azarenka 6-4, 6-4 to win the WTA Championships final in Istanbul.