Great Britain's hopes of reaching the Billie Jean King Cup final for the first time since 1981 rest on the outcome of a deciding doubles after Katie Boulter lost her singles match against Slovakia.
British number two Emma Raducanu put her team in command with a 6-4 6-4 victory over Viktoria Hruncakova in Tuesday's semi-final.
Boulter looked to secure their place in Wednesday's final by beating Slovakian number one Rebecca Sramkova afterwards.
But Britain's leading singles player lost 2-6 6-4 6-4 as the best-of-three tie went the distance.
Heather Watson and Olivia Nicholls have been called upon for the first time this week, taking on Slovakian pair Hruncakova and Tereza Mihalikova.
Italy, who are led by world number four Jasmine Paolini, await the winners.
Britain have never won the women's team event, which was formerly known as the Fed Cup and now branded the World Cup of Tennis.
Anne Keothavong's team, which also features Harriet Dart, are aiming to be the fifth British side to contest the final in its 61-year history.
At the start of the 12-nation finals in Malaga, Britain were the second-lowest ranked team and given little chance by many people on the outside of finally landing the trophy.
Keothavong, naturally, insisted from the outset that her team had the quality to be successful.
Having a pair with the pedigree of 2021 US Open champion Raducanu and top-25 player Boulter has been crucial to Britain's success.
In April's best-of-five qualifier against France - a tricky away tie on clay which British players have struggled on recently - Raducanu won both her matches with Boulter adding another to secure their progress.
The winning formula continued on the Costa del Sol.
Raducanu has not dropped a set in her three matches, providing the platform for Boulter - who has enjoyed the finest season of her career - to finish the job.
On an indoor hard court which suits her skillset, Boulter used her punishing first serve and pacy forehand to cruise past Germany's Laura Siegemund and Canada's Leylah Fernandez.
Her level against Sramkova, ranked above those opponents at 48th in the world, did not reach the same heights.
Boulter lost her way as Sramkova levelled and moved a break ahead in the decider, prompting Watson and Nicholls to start warming up for what looked like would be their first outing.
She showed tremendous fight to claw back the deficit, but then was left mortified by putting a volley into the net at 30-30 4-4.
The miss proved costly and swung momentum back to Sramkova, who continued her own 100% winning record in the finals.
Whether Britain win the trophy on Wednesday, sometime over the course of Raducanu's career, or not at all remains to be seen.
But she has again showed over the past week why Keothavong's team need her fit and firing.
Raducanu had not played for two months before the women's team event because of a foot injury and it remained to be seen what shape she would be in.
Straight-set wins against Germany's Jule Niemeier and Canada's Rebecca Marino were encouraging given her previous absence.
Raducanu was again expected to make light work of Hruncakova, who is ranked 241st in the world and largely plays on the third-tier ITF Futures Tour.
A slow start from the Slovakian, whose game revolves around power from the baseline, allowed Raducanu to move 5-1 ahead in the first set before becoming slightly passive as her opponent improved.
Her first-serve percentage was not as high as she would have liked and her returning game also lacked rhythm as Hruncakova fought back to 5-4 before Raducanu served out.
It was a similar story in the second set.
Raducanu confidently moved a double break up before Hruncakova pinched one back, forcing the British number two to again show her resilience.
The guttural roar which greeted her winning crosscourt forehand on match point indicated her satisfaction, as did the beaming smile across her face as she handed out high fives to the whole British team afterwards.
"Every match is truly challenging and as the tournament progresses it is more and more," said Raducanu, who has thrived in the team environment.
"It was a tough match and my opponent has a huge ball strike and played above her ranking.
"I was pleased with how I composed myself and served out the sets."