Karolina Muchova and Tomas Machac were in imperious form as they saw off Italians Flavio Cobolli and Jasmine Paolini respectively at the United Cup.

After Machac had defeated Cobolli 6-1 6-2 in under an hour, Muchova dispatched world number four Paolini 6-2 6-2 to seal Czechia's place in the last four.

Muchova has now won all five of her meetings with Paolini, losing just one set in the process.

"I have to find another way to play against her, of course," said Paolini, who reached the French Open and Wimbledon finals last year.

"Hopefully [the next one is] going to be better. But she's playing unbelievable."

The decisive blow for Muchova came when she broke in the longest game of the match. From there, she lost just two games, while she did not concede a single break of serve.

"I really wanted to bring a point to the team so I was trying to stay focused," Muchova said.

"Jasmine is an unbelievable player. It was a really tough match. I knew I had to go until the end. She had many break chances. I think I served well. I'm really happy I made it."

Machac, meanwhile, quipped he was playing at the same level as 24-time grand slam champion Novak Djokovic during his dominant defeat of Cobolli.

"I think this is the highest level of tennis that I can play," Machac said.

"I'm really happy to play like this in such an important moment. I was surprised how I played great without any mistakes and I didn't give him any opportunity to come back."

"I know I have this kind of level but to play and when I saw how the match was going I just tried to be strong mentally for as long as possible. I was playing like Novak!"

The Czechs will take on the United States, represented by Coco Gauff and Taylor Fritz, for a place in the final.