Kevin Anderson is pleading for Wimbledon officials to introduce fifth-set tiebreakers after outlasting marathon man John Isner in the longest grand slam semi-final in history.

The South African needed six hours and 36 minutes to see off Isner 7-6 (8-6), 6-7 (5-7), 6-7 (9-11), 6-4, 26-24 in a truly epic encounter featuring 102 aces and 96 service games but just six breaks.

The match was the second-longest in professional tennis history, behind only Isner's record-setting 11-hour, five-minute first-round Wimbledon triumph over Frenchman Nicolas Mahut in 2010.

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Anderson will have to wait to find out his opponent in the final after the other semi-final between Rafael Nadal and Novak Djokovic could not be completed due to time constraints.

The ridiculous length of the Anderson-Isner clash left Nadal and Djokovic waiting until 8pm local time before stepping on court for their box office semi-final.

The roof was closed and Nadal and Djokovic had until the 11pm club curfew to finish or return on Saturday, the traditional rest day for the two men's semi-finalists.

In the end, Djokovic won a third set tiebreak 11-9 before play was suspended with the Serbian star leading Nadal 6-4, 3-6, 7-6 (11-9).

"I don't really know what to say right now," Anderson said earlier after the first semi-final..

"Just playing like that in those conditions, it was really tough for both of us.

The crowd may have hoped for a quicker finish to the semi-final, but they gave huge support to both players. ( AP: Glyn Kirk, Pool Photo )

"John's such a great guy and I really feel for him because if I'd been on the opposite side, I don't know if I could take that, playing for so long and coming up short.

"You feel like this is a draw for the two of us, but somebody has to win.

"So I apologise if I'm not more excited right now because the mix of emotions getting through something like that is quite different."

The last set alone lasted five minutes shy of three hours and Anderson said it was unfair on both players.

"I really hope we can look at this and address this because in the end you don't even feel that great out there," the eighth seed said.

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Although the game was dominated by big serving, there were some amazing highlights, including a key moment deep in the fifth set.

The right-handed Anderson slipped and fell, but scrambled back to his feet in time to hit a return left-handed and continue the point before Isner eventually pushed a forehand just wide. Two points later, Anderson had the vital break to lead 25-24 before serving out the match.

The US Open is the only grand slam to use tiebreakers in the fifth set, with the Australian Open and French Open, like Wimbledon, both also playing advantage sets.

Twitter was abuzz with jokes that the Anderson-Isner match could well stretch beyond the 70-68 final-set scoreline that Isner won with over Mahut eight years ago.

The final set of the epic semi-final went almost three hours, as both players were pushed to the edge of their endurance. ( AP: Ben Curtis, Pool Photo )

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That "endless match" prompted officials to erect a plaque on Court 18 to commemorate the feats of the two players.

The Anderson-Isner showdown could not match that in terms of length, but the final set went for 50 games, with neither player able to achieve the breakthrough until right at the end.

Many would argue Anderson and Isner deserve similar recognition after the friends warmly embraced at the net before receiving a standing ovation from tennis's most famous centre-court crowd.

Anderson's prize for his bittersweet victory over his former US college friend and rival is a date on Sunday with Nadal or Djokovic.

Should Nadal prevail in the duo's record 52nd showdown, the Spaniard will play Anderson in a repeat of last year's US Open final in New York.

AAP/ABC