PERTH, Australia — Roger Federer relied on his trusted serve to beat Stefanos Tsitsipas 7-6 (5), 7-6 (4) Thursday and give defending champion Switzerland a spot in the Hopman Cup final.

The victory assured Switzerland's advancement, but Greece claimed a consolation 2-1 victory when Maria Sakkari beat Belinda Bencic 6-3, 6-4 in women's singles.

Greece also won the mixed doubles 4-3 (4), 2-4, 4-3 (3) in the Fast4 format.

The 37-year-old Federer's precision went up against Tsitsipas' power in the first set of the men's singles match, and not much separated the two. Eight games were held at love.

"There was very little unforced errors and it was really good quality tennis," Federer said. "It could have easily gone three sets. For me it is about maintaining a good level of play and I am happy with my game."

Federer will be going for a record third Hopman Cup title when the Swiss team faces either host Australia or Germany in Saturday's final.

"I will be excited to watch it tomorrow and see who we play in the final," Federer said. "This format lends itself to some exciting tennis."

Federer lost only seven games in wins over Cameron Norrie and Frances Tiafoe but found it tougher in his first match against Tsitsipas.

Federer trailed 4-1 in the first tiebreaker before reeling off consecutive forehand winners to claw back into it. Tsitsipas double-faulted at 5-5 and Federer then won the set with an ace.

The serve continued to dictate play until Federer had break points in the ninth and 11th games but was unable to convert. The 23-time Grand Slam champion, however, raised his game in the tiebreaker with a perfect drop shot to take a 6-3 lead. He closed it out shortly after.

Federer's appearances at the past two Hopman Cups were followed by Australian Open titles.

Earlier, Serena Williams beat Katie Boulter 6-1, 7-6 (2) to complete an unbeaten Hopman Cup campaign in singles. With daughter Alexis Olympia in attendance, Williams was made to work in the second set before prevailing.

The winless United States, however, lost to Britain 2-1. Norrie upset Tiafoe 7-6 (4), 6-0 in men's singles and Britain won the mixed doubles 3-4 (2), 4-3 (4), 4-1.

The 37-year-old Williams' hopes for a record third Hopman Cup title ended when the United States was eliminated after losses to Greece and Switzerland.

Williams has slowly built momentum in her first tournament since the US Open in September as she eyes a record-equaling 24th Grand Slam singles title in Melbourne.

"It was definitely good to play three singles matches here, and the mixed (doubles)," Williams said on-court after her singles match.

The American did not attend a news conference after the match.

AP