Defending champions Roger Federer and Belinda Bencic of Switzerland beat Americans Serena Williams and Frances Tiafoe 4-2, 4-3 (5-3) at Perth's RAC Arena on Tuesday in what had been the most highly anticipated match of this year's Hopman Cup, an annual mixed-team tennis tournament.

This was the first time that Federer and Williams, who are now both 37 and have a total of 43 Grand Slam single titles between them, had ever faced each other on the court, and after the match the two legends paid tribute to each other.

Williams said it was "super cool" that they did finally get to play against each other.

"The guy is great, he's the greatest of all time. Both on and off the court he has such charisma," Williams said.

For his part, Federer described Williams a "great champion."

"I was nervous returning. People talk about her serve so much and I see why it is such a wonderful serve because you just can't read it," he said.

The victory for Federer and Bencic meant that Switzerland defeated the United States 2-1 in their round-robin Group B session after Federer had beaten Tiafoe 6-4, 6-1 and Williams had overcome Bencic 4-6, 6-4, 6-3 in their singles matches. 

Eight countries are competing in two groups at the tournament, which serves as a warm-up to the first Grand Slam event of the season, the Australian Open in Melbourne.

On Wednesday, Germany's Angelique Kerber and Alexander Zverev face France's Alize Cornet and Lucas Pouille of France, while Australians Ash Barty and Matt Ebden take on Garbine Muguruza and David Ferrer of Spain. 

pfd/ (dpa, Reuters, AFP)