Jelena Jankovic reached the semi-finals of the Sony Ericsson Open after world number 11 Elena Dementieva retired with a back injury.

Jankovic was suffering badly from a cold herself but did not have to stay on court for too long as Dementieva quit midway through the second set.

The Serbian was leading 6-1 3-1 when Dementieva, who had her injury treated on court earlier in the match, decided she could not carry on.

"I'm fighting. I'm sick," Jankovic said. "I cannot play, I cannot breathe on the court. I don't want to go on to the court. But I'm hanging in there and trying to be strong.

"I'm more focused than usual because I know that I'm not 100 percent with my health. I'm coughing a lot. My nose is running."

Jankovic, who earlier in the tournament saved five match points against Sweden's Sofia Arvidsson in the second round, will play the winner of the all-Russian quarter-final between Dinara Safina and Vera Zvonareva.

"I was dictating the points, I didn't let her play her game," the world number three said.

"But, unfortunately, she stopped the match in the middle of the second set, and there's nothing I could do."

Dementieva struggled from the outset, racking up 26 unforced errors and was broken three times before retiring.

"I couldn't play because I felt like it was just getting worse, the back problem. It just started yesterday," the Russian said.

"I tried to do some treatment, to get some massage to relieve the pain, but it didn't help me a lot."

Reuters