The Russian fourth seed lost an epic semi-final, the longest in the history of the women's tournament, 6-7 (4/7), 7-5, 8-6 to the two-time champion and wasted a match point in the 10th game of the decider.

'It's not easy to fight against her. She's a great champion and she served so well that I wasn't sure if I was facing Serena Williams or Andy Roddick out there,' said Dementieva, who lost to Venus Williams at the same stage in 2008.

'Her first serve percentage was huge, she was serving around 120mph.'

Olympic champion Dementieva, whose best Grand Slam performances remain runners-up spots at the 2004 French and US Opens, said she regretted her choice of shot on match point when she led 5-4 in the final set.

With Williams approaching the net, the Russian went cross-court, rather than down the line, and the American gleefully accepted her opportunity with a simple saving backhand.

'That's my only regret. I should have taken more of a risk by going down the line,' said the 27-year-old.

'A passing shot is my favourite shot to make. Maybe it was all too quick. I didn't see that she was moving to cover the cross-court. I should have gone down the line or even used a lob.' -- AFP