Frances Tiafoe and Taylor Fritz set up an all-American US Open semi-final on Tuesday as compatriot Emma Navarro reached the women's last four to boost home hopes of a title sweep.

The 20th seed Tiafoe progressed when ninth-ranked Grigor Dimitrov suffered an injury in the third set of their quarter-final and quit in the fourth with the score at 6-3, 6-7 (5/7), 6-3, 4-1.

Tiafoe also made the last four in 2022 while Fritz reached his first Grand Slam semi-final by defeating fourth-seeded Alexander Zverev 7-6 (7/2), 3-6, 6-4, 7-6 (7/3).

Navarro, playing in front of her home New York crowd, broke through to a maiden Slam semi-final by defeating Paula Badosa of Spain 6-2, 7-5 after coming back from 5-1 down in the second set.

She will tackle world number two and reigning Australian Open champion Aryna Sabalenka, who brushed aside Olympic gold medallist Zheng Qinwen 6-1, 6-2.

With Tiafoe and Fritz clashing on Friday, the US is guaranteed a home men's finalist for the first time since 2006 when Andy Roddick was defeated by Roger Federer.

Roddick remains the last American man to capture a Grand Slam when he claimed the 2003 US Open.

"It's not the way I wanted to win even if I'm happy to get through to the semi-finals," said Tiafoe of Dimitrov's injury.

"It was a very high-level match. You're going to see me against another American, it's going to be great.

"It will be the biggest match of our careers."

- 'Job's not done' -

Dimitrov, 33, sought treatment off court after the third set but was reduced to walking pace in the fourth as his hopes slipped away.

The Bulgarian was reluctant to discuss the specifics of his injury after a thigh problem forced him to also quit his last-16 match at Wimbledon in July.

"I think it's a combination from everything. I think there's really no point to talk about that. It's just the game, and I need to keep my head up," he said.

Zverev's defeat to Fritz means world number one Jannik Sinner is the only top-four player left in the men's draw following the shock early exits of Novak Djokovic and Carlos Alcaraz.

"I have had a few looks at Grand Slam quarter-finals over the years so I felt it was my turn to take a step further," said the 26-year-old Fritz, who cracked 12 aces amongst his 45 winners in his victory.

"It's cool I'm in the semis. But I very much have the mindset of the job's not done."

Germany's Zverev had been attempting to reach his ninth semi-final at the Slams and third in New York.

"Terrible. Just absolutely terrible by me," he said of his performance. "I did nothing to deserve the win, simple as that."

- 'Complete disaster' -

Navarro insisted she always believed she could claw her way back from a 5-1 second- set deficit against New York-born Badosa.

"When I got to 5-2 I had an inkling that I'd win in two sets," said Navarro, who had lost in the first round on her only other two appearances at the tournament.

"I was a complete disaster today," said Badosa after committing 35 unforced errors.

Zheng was bidding to become the third Chinese woman to reach the US Open semi-finals after Li Na in 2013 and Peng Shuai in 2014.

However, she was completely outplayed by Sabalenka in a 73-minute loss in which she hit just nine winners.

Zheng said the record late finish to her last-16 clash which finished at 2:15 am on Monday had impacted her performance. She said she only went to bed at 5:00 am.

"I couldn't sleep after I finished the match 2:30 in the morning. I'm not able to practice yesterday because I was feeling terrible," said Zheng.

The 26-year-old Sabalenka, runner-up to Coco Gauff in New York last year, will be playing in her fourth successive US Open semi-final and ninth at the Slams.

The Belarusian also defeated Zheng at the same stage of the US Open in 2023 before going on to beat the 21-year-old again in the Australian Open final in January.

"It was important that I got the early break, that was an advantage because it's tough to face her," said Sabalenka.