The first match of the day in front of a record crowd of 14,029 at Perth Arena saw 19-time Grand Slam champion Roger Federer beat world number eight Jack Sock in straight sets 7-6, 7-5.

Federer took the opening game in just 70 seconds but his 25-year-old opponent managed to stay within touching distance throughout the first set with Federer requiring a tie-break to secure the opener.

Sock kept up his good form in the second set and it looked like there would be another tie-break with the score reading 5-5 following some sumptuous shots.

World number two Federer, however, managed to break his opponent’s serve to make it 6-5 before closing out the match by holding onto his own.

After the match, Federer, who has yet to drop a single set against Sock in their five meetings, said: "I haven’t seen it again, but all I remember are the last two shots.

"The rest of it is a blur, I’d like to see it again.

"It was a lot of fun."

Federer’s compatriot Bencic also won in straight sets in her match against world number 10 CoCo Vandeweghe, 7-6, 6-4.

The 2014 US Open quarter finalist raced into a 4-1 lead in the opening set, but 26-year-old Vandeweghe, coached by 1987 Wimbledon Champion Pat Cash, then stormed back, securing four straight games to take a 5-4 lead.

Bencic recovered to take the set to a tie-break, eventually securing it 7-6.

The second set was remarkably similar with Bencic again going 4-1 up before Vandeweghe won two straight games to make it 4-3.

Former world number seven Bencic managed to stop her opponent’s momentum to close out the set, and the match, 6-4.

Bencic and Federer then combined to beat Sock and Vandeweghe in the mixed doubles, 4-3, 4-2.

After securing their 100 per cent record over the course of the tournament, Bencic said: "Last year we were so close to getting into the final, I’m so relieved now.

"Playing for your country is very special, whether it’s Fed Cup or Hopman Cup.

"I’m proud when I represent Switzerland and I hope we can do well in the final too."

Switzerland are set to play either Belgium or Germany in Saturday’s final.

Earlier in the day, Russia won their dead rubber match against Japan, 2-1.

Japan’s Naomi Osaka, who has never been beyond the third round of a Grand Slam, had given her side the lead with a 6-4, 3-6, 7-6 win against 2016 Olympian Anastasia Pavlyuchenkova in the women's singles.

Russia’s Karen Khachanov, a silver medallist at the 2014 Summer Youth Olympic Games in Nanjing, restored parity with a 6-4, 6-2 win against Yuichi Sugita in the men’s singles match.

The Russians then sealed their overall victory with a comprehensive 4-1, 4-0 win in the mixed doubles.

Tomorrow sees the final round of group matches take place with Belgium taking on Canada and Germany facing hosts Australia.