Liudmila Samsonova started the match for the RTF against 2017 US Open champion Sloane Stephens in the Czech Republic.

Stephens was formidable in the first set, winning 91 per cent of her first-serve points and 100 per cent of her second-serve points.

The 28-year-old scored 28 points, double that of her opponent, to win 6-1 in 26 minutes.

Samsonova then produced the tennis that saw her win the German Open in June.

Despite serving three double faults, the world number 40 drew level with a 6-4 second set win before closing out a thrilling win with a 6-3 victory in the third and final set.

Danielle Collins pulled it back for the US in the second fixture, beating Anastasia Pavlyuchenkova 6-7, 7-6, 6-2.

The match was neck and neck throughout the first two sets before Collins ran away with it in the third.

Pavlyuchenkova was extremely wasteful on key points, winning just three of 12 break points.

The result left the match to go down to a doubles showdown between the RTF's Veronika Kudermetova and Samsonova and Shelby Rogers and CoCo Vandeweghe.

It was a clinical display from the RTF as they crushed their opponent 6-3, 6-3, in 1 hour 13 minutes.

"I can't even describe what it feels like," tweeted Samsonova.

"Today is one of the most exciting and important days of my entire life!

"We are in the final of [the] BJK Cup.

"Proud and overjoyed."

In the later match, Switzerland outclassed Australia 2-0 to reach the final for the first time since 1998.

World number 39 Jil Teichmann defeated Storm Sanders 6-0, 6-3 in a little over an hour in a victory characterised by seven monstrous aces.

Tokyo 2020 gold medallist Belinda Bencic then put the nail in Australia's coffin with a 6-3, 6-2 win over Ajla Tomljanovic.

RTF and Switzerland will go head-to-head in tomorrow's final.