Roger, Maria in final

Roger Federer fought through the longest three-set singles match in the Open era Friday when he beat Argentina's Juan Martin del Potro 3-6, 7-6 (7/5), 19-17 to reach the Olympic final.
Maria Sharapova swept into her first Olympic final as the Russian world number three defeated compatriot Maria Kirilenko 6-2, 6-3 in the semifinals.
The 25-year-old will play Wimbledon champion Serena Williams or world number one Victoria Azarenka in Saturday's final as she tries to complete the Golden Slam of titles in all four majors and the Olympic singles.
Sharapova is competing in the Games for the first time and the French Open champion is now guaranteed at least a silver medal following her dominant display against the 14th seed in a clash clashing one hour and 29 minutes on Wimbledon's Court One.
If Sharapova felt slighted by tournament organisers, who chose her match as the only one of the four men's and women's singles semi-finals to be scheduled on Court One, she didn't show it.
This was a composed display from the moment she landed the first blow with a break to love in the sixth game of the first set.
Sharapova pressed home her advantage with another break to take the set in convincing fashion.
Wimbledon champion Federer was on the brink of a shock defeat on Centre Court after dropping the first set, but the world number one finally subdued del Potro after a marathon four hours and 26 minutes.
The match, 23 minutes longer than Rafael Nadal and Novak Djokovic's Madrid semifinal in 2009, comes after Jo-Wilfried Tsonga took 66 games to beat Milos Raonic in the second round -- the most seen in an Olympic three-setter.
The great escape means Federer, 30, is guaranteed at least a silver medal. In Sunday's final, he will face world number two Novak Djokovic or Britain's Andy Murray, who was beaten by Federer in last month's Wimbledon final.
After a relatively barren two years by his standards, Federer is suddenly enjoying another of his dominant periods and this hard-fought victory showed his hunger for success remains as strong as ever.
Less than a month ago, Federer, a doubles gold-medallist with Stanislas Wawrinka in Beijing four years ago, was crowned Wimbledon champion for a record-equalling seventh time.
Now he is just one win away from completing the 'golden slam' of titles in all four majors and the Olympic singles gold.
Del Potro's 2009 US Open final win over Federer was one of just two victories in 14 meetings with the Swiss, who came from two sets down to beat the 23-year-old in this year's French Open quarter-finals.