LONDON: Switzerland's Roger Federer had to break yet another record to keep his Olympic dream alive and Andy Murray surfed a wave of British euphoria at Wimbledon on Friday to set up a mouthwatering showdown for a gold medal.

Federer outlasted Argentina's Juan Martin del Potro in the longest best-of-three-set set match ever played in men's professional tennis, eventually winning 3-6 7-6 19-17 in four hours 26 minutes to reach his first Olympic singles final.

Murray's clash with Serbia's Novak Djokovic was no less intense, if not as long, as the Scot was roared to a 7-5 7-5 victory by a flag-waving crowd drunk on the joy of a magnificent three days for British rowers, canoeists and cyclists.

“It's just an amazing atmosphere to play in,” an emotional Murray, who on Sunday has the chance to avenge a heart-breaking loss last month in the Wimbledon final to world number one Federer, told reporters.

“We play in tennis tournaments around the world and we get good crowds and the support is good, but you cannot compare it to that. The court was going nuts at the end and it was so loud.

“I haven't experienced noise like that on a tennis court.”

The women's singles semi-finals were tame by comparison with Serena Williams, who like Federer has won everything in tennis apart from an Olympic singles gold, continuing to make mincemeat of whoever stands the other side of the net.

This time it was Belarusian Victoria Azarenka who was made to suffer as the American won 6-1 6-2 in 63 minutes.

Forced to wait for Federer and Del Potro to complete their titanic struggle, Wimbledon champion Williams made up for lost time once she got on Centre Court, barely giving the world number one a sniff in a one-sided match.

“I warmed up probably five or six times. But I can wait with the best of them,” 14-times grand slam singles champion Williams, whose later women's doubles semi-final with sister Venus was postponed, told reporters.

“I have been waiting my whole life.”

She may not have to wait too much longer to complete the “golden slam” - all four majors and an Olympic singles gold - although Maria Sharapova will be a formidable opponent on Saturday as she also looks to complete that rare collection.

Sharapova was too strong for Maria Kirilenko in an all-Russian semi-final, winning 6-2 6-3 in around an hour.

“Well it's incredible, not only to be part of this event and be an Olympian, but to put yourself in with an opportunity to go for gold. It's a really nice feeling,” Russia's flag bearer Sharapova, competing at her first Games, told reporters.

GOLDEN CURRENCY

While Williams and Sharapova are both great champions, their efforts were overshadowed by Federer and Murray on Friday.

Olympic gold medals transcend conventional currency and all have equal merit but if their worth was measured in sweat alone, the one that goes around the neck of Murray or Federer on Sunday would be the most treasured.

While Murray is yet to win a grand slam title, Federer, who has 17 of them, knows that this is his last chance to win an Olympic singles title to go with the doubles he won in Beijing.

The fact that it is at Wimbledon eggs the cake even more.

Yet, for long periods on Friday, Del Potro was grinding Federer's hopes into Centre Court's dusty baselines, overpowering the Swiss in a 36-minute first set.

Even after leveling the match he was perilously close to losing, serving to stay alive on no less than 12 occasions.

“I mean, emotionally obviously I'm extremely drained from serving to save the match so many times,” 30-year-old Federer, who owns virtually every record in the book, told reporters.

“Basically I was down in the score for the entire match except the one time where I served for it.”

“I definitely got a sense that this was something special we were both going through, with Juan Martin,” added Federer, who served for the match at 10-9 in the 163-minute decider after gaining a break only to drop serve to love.

“The deeper we went into the match, the more I thought, Wow, this is so cool to be part of a match like this. I feel bad and horrible for Juan Martin but he can be very proud.”

With del Potro tiring, Federer got another break at 17-17, long after they had overtaken the Rafa Nadal and Djokovic's previous longest three-setter, and this time, despite wasting one match point with a nervy volley, ended the contest.

“The emotions I felt were as strong as winning a grand slam almost,” Federer said.

Del Potro looked distraught.

“It hurts a lot,” he said before his day got even worse as he and partner Gisela Dulko were beaten in the mixed doubles quarter-finals by American duo Mike Bryan and Lisa Raymond.

Earlier Bryan, along with twin brother Bob, reached their first Olympic men's doubles final with a 6-4 6-4 victory over French duo Julien Benneteau and Richard Gasquet.

After returning from Beijing four years ago with a pair of bronze medals, the world's top doubles pair will face France's Jo-Wilfried Tsonga and Michael Llodra on Saturday after they also won a marathon, beating Spain's David Ferrer and Feliciano Lopez 6-3 4-6 18-16.

“Every sports fan in the world knows what an Olympic medal is. They don't necessarily know what a Wimbledon title is,” the 34-year-old Californian, an 11-times grand slam doubles champion, told reporters of the importance of Olympic gold.

“It would be at the front of the trophy case for sure.”