Nerveless USA No.1 Clervie Ngounoue admitted to feeling unbeatable after her side initiated a stunning comeback to overcome Japan and secure a place in the ITF World Junior Tennis semi-finals in Prostejov.

With Japan leading 1-0, Ngounoue recovered from a set down to defeat Mio Mushika before joining forces with Tsehay Driscoll and guiding the USA to the last four following a match tiebreak in the doubles, which they won 10-7.

Seven-time champions USA will now play top seeds Switzerland tomorrow for a place in the final and the chance to regain the trophy they last won in 2017. For Ngounoue, who has won all six rubbers she has contested this week, her status as her nation’s No. 1 player is certainly proving an inspiration.

“I feel amazing – invincible almost,” Ngounoue told itftennis.com. “After my singles I just thought: ‘I’m No. 1 on this team for a reason’. I love competing and I just blocked the feeling of tiredness out. I wanted to win the doubles, I wanted to take it – that’s what drove me.”

On the eve of USA’s showdown with Japan, captain Maureen Diaz likened Ngounoue to American sensation Cori Gauff, who reached the fourth round at Wimbledon in July. The 13-year-old welcomes such comparisons.

“Some of the things I have done remind me of Coco also, and I definitely look up to her as my idol,” added Ngounoue. “We’re friends but I look at her like she is everything. I watch her a lot: her fitness and practice. It really motivates me.”

Serbia squeezed through to the knockout phase by the skin of their teeth on Wednesday and threatened an upset against Switzerland as Tijana Sretenovic defeated Karolina Kozakova 7-5 6-4 in the opening singles rubber.

Celine Naef restored parity by overcoming Lola Radivojevic 6-4 6-2 before Switzerland, conquerors of European qualifying, sealed their passage to the semi-finals as Kozakova and Naef prevailed in the doubles.

In the other half of the draw, Canada surged over the line courtesy of a successful doubles showing by Kayla Cross and Victoria Mboko, who steered their nation to victory by defeating Ukrainian pair Daria Yesypchuk and Anna Vashchenko 7-5 6-3. It is the first time since 2013 that Canada have reached the semi-finals, where they will face No. 2 seeds Czech Republic.

It is the third tie in succession that Cross and Mboko have united to great effect in the decisive set. Mboko told itftennis.com: “Kayla kills really well at the net and I have a strong game at the baseline. The doubles is a strong suit for us – our games match up well."

Cross had earlier ensured that Canada made the perfect start to the clash, dispatching Vashchenko 6-1 6-0, before Yesypchuk levelled matters by overcoming Mboko 7-5 5-6 6-2. Cross, who has won three of her four singles rubbers at the tournament, insists she is relishing the prospect of facing a formidable Czech Republic outfit tomorrow.

“I haven’t played any of them before and I’m excited to test myself against them,” she said. “We’re delighted to be in the semi-finals. It is a really great experience being here and nice to play as a team. Usually you’re all alone so it’s really good to have team-mates and support.”

The only main draw tie in the girls’ division not to be settled by the doubles was the showdown between Czech Republic and the Philippines, which the hosts won in convincing style, 3-0.

The juggernaut which is Brenda Fruhvirtova continued her relentless procession on the clay of the TK Plus Arena by defeating Alexa Joy Milliam 6-1 6-1. The Czechs also tasted doubles success, but not before Nikola Bartunkova had dispatched left-hander Alexandra Eala 6-2 7-5.

In the play-off draw, meanwhile, there were victories for Italy, China, Greece and Korea over Brazil, Egypt, South Africa and Venezuela respectively.