Roger Federer secured a return to the Hopman Cup final for Switzerland by defeating Greece's Stefanos Tsitsipas in straight sets on Thursday.

Greece needed to defeat the defending champions 3-0 in Perth to reach the showpiece and Federer put paid to their hopes in the first match of the tie with a 7-6 (7-5) 7-6 (7-4) triumph.

Tsitsipas made a strong start to the first-set tie-break at RAC Arena and surged into a 4-1 lead, but 20-time grand slam champion Federer rallied back to draw level.

A double fault from the world number 15 handed Federer a set point he converted, although the Greek did well to stave off three break points and take the second set to a tie-break.

Federer produced an exquisite drop-shot to set up three match points and book Switzerland's place in the final against Australia or Germany, who meet on Friday.

"I thought Stefanos came out and played a great match, so did I, very little unforced errors, just really good quality tennis," said Federer in his post-match interview.

"It could have easily gone three sets. I enjoy playing the young guys, they bring something different, something I've never seen before, and that was the case today."

He added with a smile: "You can see I'm still breathing heavily. I'm not getting any younger."

Serena Williams won her singles rubber against Katie Boulter 6-1 7-6 (7-2) but the United States fell to a 2-1 loss against Great Britain.

Despite the USA's failure to make it out of the round-robin stage, Williams won all three of her individual outings as she gears up for the Australian Open.

"It was definitely good to play three singles matches here, not to mention the mixed [doubles]," said Williams.

Cameron Norrie overcame Frances Tiafoe 7-6 (7-4) 6-0 before he and Boulter defeated their American counterparts 3-4 (2-5) 4-3 (5-4) 4-1 in the mixed doubles.