The Czechs, looking for a third consecutive title in the competition, were outplayed in Palermo where former Wimbledon champion Petra Kvitova was beaten by Roberta Vinci to leave them needing to win every match on Sunday.
In Moscow, an inspired Dominika Cibulkova came from a set down to beat Anastasia Pavlyuchenkova 5-7 6-1 6-4 in the opening match, lasting two-and-a-half hours, before 75th-ranked Daniela Hantuchova made short work of Maria Kirilenko 6-2 6-4 in the second singles to put Slovakia in command.
The Slovaks are making their first semi-final appearance since 2002 when they went on to win their only title to date.
After dropping the first set, world number 13 Kirilenko led 2-0 in the second before her game fell apart on red clay in the outskirts of Moscow as Hantuchova took complete control, sealing the match with a crisp cross-court forehand.
"I have enough experience to deal with tough situations," said former top 10 player Hantuchova, who has slipped in the rankings in the last few years.
"This is the Fed Cup and we were playing as a team here."
Earlier, world number 15 Cibulkova secured a key break in the seventh game of the deciding set for a 4-3 lead before clinching victory on her first opportunity when Pavlyuchenkova's lose forehand sailed wide.
"It was a very, very tough match especially playing in a foreign country," Cibulkova told reporters.
"I was very nervous at the beginning, was making a lot of errors, double faults, but gradually I got back into the match. I was telling myself not to give up, to keep fighting. This inner strength has helped me win this match."
In the other semi-final world number seven Sara Errani got the Italians off to a great start with a 6-4 6-2 defeat of Lucie Safarova. Then, Vinci stunned Kvitova 6-4 6-1.
Kvitova, who had won 13 of her last 14 singles rubbers in the competition, was no match for Vinci with her superior power unable to make any impact on the slow Palermo clay.
Kvitova, who will play Errani in the first reverse singles, said she had struggled to adapt to clay.
"I hope I can cancel this match in my mind and have a free mind for tomorrow," Kvitova said on Saturday. "I'm still getting better, and it's obviously tough to be 100 per cent ready to play these girls on clay but we'll see."
Italy are looking to reclaim the title they won in 2009 and 2010 but captain Corrado Barazzutti was urging caution.
"Tomorrow is another day," he said. "We played fantastic today and it was really important that Roberta beat Petra but we have to stay focussed."
- Sports & Recreation
- Roberta Vinci
- Petra Kvitova
- Dominika Cibulkova
- Daniela Hantuchova
- Anastasia Pavlyuchenkova
- Maria Kirilenko