The world number two maintained an unblemished record in five clashes withthe eighth-ranked Sock, beating the American in straight sets as Switzerland beat the United States 3-0 to advance to Saturday's final.

Their opponent will be decided on Friday, with Germany and Belgium the leading contenders.

Federer had not dropped a set in four previous matches against Sock, but had to produce some of his very best to keep the American at bay and give the Swiss the early lead in the Group B tie.

Belinda Bencic's superb form continued when the world number 74 then upset 10th ranked CoCo Vandeweghe to secure the tie and put the Swiss into the final.

The dead mixed doubles rubber was extremely light-hearted, with the Swiss winning in straight sets.

Federer is aiming for a second Hopman Cup title, having also won the tournament back in 2001, before he had won an ATP singles title, when he partnered with Martina Hingis.

The 36-year-old also opened his 2017 campaign at the Hopman Cup, following which he ended an almost four-year Grand Slam drought with a shock fifth triumph at the Australian Open in Melbourne.

Speaking after the 7-6 (7/5) 7-5 win over Sock, the 19-time Grand Slam champion said where he was uncertain heading into 2017, as he returned from a knee injury, he enters 2018 brimming with confidence.

“Yes, you could say that,” he said when asked if his confidence was higherthan at the same time last year.

“I think I'm more secure… I was 17 in the world as well, it does make a difference,” he added.

“If I wasn't going to win a match in Australia, or win two matches, I was going to drop out of the top 30, so things were a little bit on edge last year.”

Federer has at times toyed with his opponents in winning his three singles matches without dropping a set, and is a step ahead of his Hopman form last year when he was beaten by German young gun Alexander Zverev.

Having already beaten lower-ranked duo Yuichi Sugita of Japan and Karen Khachanov of Russia this week, he said the challenge of facing Sock was a perfect one at this stage of his Australian Open preparation.

“I thought it was a very entertaining match, a high-quality level match and the right step forward for both of us,” Federer said.

As brilliant as the Swiss star was, Sock was left ruing some missed chances, particularly when he held break points in the ninth and 11th games of the first set.

He was only broken once, in the 11th game of the second set, after Federer produced some stunning defence under pressure.

“He came up with an unbelievable point to break in the second set,” Sock said.

“I had chances to win the first set or get up a break and then serve for it and was in there in the second obviously as well.”

Bencic then continued her impressive week by claiming her second top-20 scalp in beating Vandeweghe in straight sets, having also disposed of the 15th-ranked Anastasia Pavlyuchenkova.

Herself on the comeback trail after injury issues, the former world number seven maintained her perfect record in singles to win 7-6 (8/6), 6-4 and was delighted to have put the Swiss into the final.

“We were so close last year,” she said. “I am relieved we made it.”

In the earlier tie on Thursday, the Russian pairing of Khachanov and Pavlyuchenkova beat Japan's Sugita and Naomi Osaka 2-1, with both teams already out of contention for the final.