Novak Djokovic limited big-serving Ben Shelton to five aces and broke him five times in their US Open semi-final on Friday.

Djokovic pushed back when the 20-year-old unseeded American produced a late stand that got the home crowd into the match.

And after overcoming what he called "a little black hole" caused by tension to right himself, finish off a 6-3, 6-2, 7-6 (4) victory and reach his record-tying 10th final at Flushing Meadows and 36th at all major tournaments, Djokovic added a touch of insult to injury by mimicking the kid's "Hang up the phone!" celebration gesture.

Djokovic then pointed to his temple and pounded his fist on his chest, before a stone-faced Shelton met him at the net for the most perfunctory of handshakes.

A year after Djokovic could not travel to the United States for the Open because he is not vaccinated against Covid-19, the 36-year-old from Serbia is one victory away from a fourth title in New York and 24th Grand Slam championship overall.

"Well, fact is that, at 36, every Grand Slam final ... could be the last one. So I think that I probably value these occasions and opportunities to win another Slam more than I have maybe 10 years ago,” said Djokovic, who would be the oldest man to win the US Open in the professional era, which began in 1968.

"I don't know how many I have ahead of me now.”

He has made it to the finals of all four majors this season, with victories at the Australian Open in January and French Open in June.

On Sunday, Djokovic will face 2021 US Open champion Daniil Medvedev, who advanced by eliminating defending champ Carlos Alcaraz 7-6 (3), 6-1, 3-6, 6-3 in the second semi-final later on Friday night. Medvedev denied Djokovic a calendar-year Grand Slam by beating him in the final at Flushing Meadows two years ago.

Both men played brilliantly in parts, so-so in others. Both interacted with the spectators, pointing to an ear to ask for more noise.

If Djokovic does end up leaving with the hardware this time, he would break a tie with Serena Williams for the most major singles championships in the Open era.

"It's another shot for history," said Djokovic, who was seeded No. 2 at the US Open but will replace Alcaraz at No. 1 next week no matter what happens on Sunday.

Djokovic vs. Shelton certainly seemed like a mismatch beforehand: Djokovic was participating in his record 47th Slam semifinal and his 100th US Open match; the 47th-ranked Shelton was in his first major semi and only his seventh career match at the Open.

Shelton won an NCAA singles title for the University of Florida last year and captured attention over the past two weeks with the powerful swings of his racket that generated a tournament-high 76 aces entering Friday, his shouts of "Yeah!” or biceps flexes after winning points and a victory-capping pantomime pretending his hand is an old-style telephone handset that he slams down.

"I thought it was very original, and I copied him," Djokovic said with a smile. "I stole his celebration."

Shelton actually borrowed it from former Florida track and field athlete Grant Holloway, a world champion hurdler.

Shelton insisted Djokovic's end-of-match gesture didn't bother him.

"I don't like when I'm on social media and I see people telling me how I can celebrate or can't celebrate. I think if you win the match, you deserve to do whatever you want,” Shelton said.

"As a kid growing up, I always learned that imitation is the sincerest form of flattery, so that's all I have to say about that."

He made things interesting in the third set, lifting his level of play as Djokovic got tight when the finish line neared. Shelton broke for the only two times in the match, even held a set point at 5-4 and later erased a match point on the way to forcing the concluding tiebreaker.

The fans loved it.

"It was loud," Shelton said. "I mean, really loud."

But Djokovic, always so tough when the going gets tough, pulled out the win.

The retractable roof was closed because of rain in the forecast, creating echoes for the soundtrack of yells and applause in Arthur Ashe Stadium, where there were additional police officers and security guards a day after four climate protesters — including one man who glued his bare feet to the concrete in the stands — caused a 50-minute delay during Coco Gauff's semi-final victory.

In his sleeveless muscle shirt, Shelton came out smacking his high-rate lefty serves. After one at 140 mph (226 kph), he shook his racket. After an ace at 145 mph (233 kph), he screamed.