Victory over the Czech Republic on the opening day of the tournament had boosted Vandeweghe and Sock’s chances of progression from Group B of the tournament, which sees one male and one female player compete for their nation.

Vandeweghe cruised to a 6-2, 6-4 victory in the opening match of the day, defeating Spain’s Lara Arruabarrena.

A second successive triumph for Sock followed, with the American coming from a set down to win his men’s singles rubber 3-6, 6-2, 6-3 against Feliciano Lopez.

The Americans then combined to whitewash their Spanish opponents by winning 4-3, 3-4, 4-3 in the Fast4 mixed doubles format, where sets are determined on a first-to-four-games basis.

Their progression to the semi-finals was confirmed when Kyrgios and Gavrilova were beaten for the second group match in a row.

Despite the defeat, Kyrgios remains unbeaten in men’s singles matches at the tournament having beaten the Czech Republic’s Adam Pavlasek 7-5, 6-4.

The Australian sought to play down concerns over a knee injury, which he claims will not hinder his preparations for the Australian Open later this month.

Kyrgios recently returned from a suspension, which was imposed by the Association of Tennis Professionals (ATP) following an investigation into his conduct at the Shanghai Masters, where he was accused of not trying.

He was initially banned for eight weeks from competing in tournaments, but his sanction was reduced to three after he agreed to work with a sports psychologist.

A surprise 4-6, 6-4, 6-4 loss for Gavrilova against Lucie Hradecka, the world number 166, had put Australia’s hopes of reaching the semi-finals under threat.

The Czech Republic would end the home duo’s ambitions to defend their title in the mixed doubles, as a  3-4, 4-2, 4-2 win confirmed their 2-1 triumph.

Hradecka and Pavlasek remain in contention for a last four spot, with the pair set to meet Spain on Thursday (January 5) to decide who progresses from Group B with the US.