World number one Jelena Jankovic maintained her red-hot form to remain on course for a third title in succession at the Kremlin Cup.Pennetta led 3-0 in the first set tie-break, but lost all her momentum with a double-fault and Jankovic stole it 8-6.
The Italian then had chances to go 4-2 up in the second set during a game of 12 deuces, but Jankovic clung on and broke her spirit - finally running out a straight-sets winner.
Dementieva beat fellow Russian Nadia Petrova 6-4 4-6 7-6 (8-6) to clinch her berth in tomorrow's semi-final.
Assessing Jankovic's form, Dementieva said: "She is the strongest player in the world. She's playing terrific tennis and has just won back-to-back titles on different surfaces and in different parts of the world.
"It won't be an easy match. It will be interesting for me to challenge her."
