Novak Djokovic and Andy Murray set up a blockbuster Wimbledon final showdown after both survived tough matches on an epic day of semi-finals on Friday.

World No.1 Djokovic reached his 11th grand slam final by beating Argentine eighth seed Juan Martin del Potro in a thrilling five-set encounter, the longest Wimbledon semi-final in history.

Murray joined him after beating Polish 24th seed Jerzy Janowicz 6-7 (2-7) 6-4 6-4 6-3 in a match that finished under lights after 9.30pm local time.

The Scottish world No.2, trying to become Britain's first male champion at Wimbledon since 1936, will get another crack at winning his home slam after losing the final to Roger Federer last year.

"I'm obviously delighted with that," Murray said after his win.

"He (Janowicz) is very talented and very unpredictable, hit some huge serves out there, and gave me very little rhythm so I'm very glad to get it done and get another chance at playing in another final."

Murray survived an early pummelling from Janowicz and then a controversial decision to shut the Centre Court roof due to bad light when he had just taken a two-sets-to-one lead.

The Scot was furious with Janowicz, who had been pleading for the roof to be shut, and referee Andrew Jarrett, claiming there was still time to finish the match in daylight.

But he returned to finish the job, sealing the win in two hours and 52 minutes.

It set up fourth meeting in a grand slam title matches between he and Djokovic, with Murray hoping for a repeat of his triumph in the 2012 US Open final.

The pair have met only once before on grass, with Murray triumphing in the semi-finals of the London Olympics last year.

"It'll be a tough match. He and Del Potro played an incredible match today," Murray said.

Serbian star Djokovic earlier clinched an epic 7-5, 4-6 7-6 (7-2) 6-7 (6-8) 6-3 win over a gallant Del Potro.

Over four hours and 43 minutes, Djokovic squandered two match points in the fourth set tiebreaker before going on to earn a shot a seventh grand slam crown.

The top-seeded Serb fired 80 winners and he hopes his flair for dramatic encounters will prove crucial in the final.

Friday's win represented the seventh time in the his last eight majors that he has taken centre stage in a marathon five-set match.

At the French Open semi-final last month, he lost in five sets to Rafael Nadal while also being pushed all the way by Stanislas Wawrinka in the fourth round at the Australian Open.

He played a five-set final in defeat to Andy Murray in New York last year, two marathons at Roland Garros against Andreas Seppi and Jo-Wilfried Tsonga after starting 2012 with his record 5hr53min final triumph over Nadal in Australia.

His sequence began at the 2011 US Open in his semi-final win over Roger Federer.

"I've had some epic matches in my career and some long five setters. Especially the one that stands out is the final with Nadal at the Australian Open last year. It went for six hours," said Djokovic.

"But I have the experience of playing long matches, and I know that I have been pushed to the limit today, as my opponent was also.

"It was one of the most thrilling matches that I have ever played, especially here in Wimbledon."