Updated

Czech qualifier Petra Cetkovska stunned up Li Na in Friday's semifinal action at the $618,000 New Haven Open tennis event, a final U.S. Open tuneup.

The world No. 40 Cetkovska outlasted the second-seeded world No. 7 Li 6-2, 5-7, 7-6 (11-9) on the hardcourts at Yale University. The 26-year-old Cetkovska will now appear in her first-ever WTA final.

The Czech needed 2 hours, 41 minutes to pull off the upset, which she did despite piling up 10 double faults on Day 6. The sloppy match featured 13 service breaks, including seven by Cetkovska.

Cetkovska will meet the Caroline Wozniacki-Francesca Schiavone winner in Saturday's finale. The world No. 1 Wozniacki is gunning for her fourth consecutive title at this tournament. She defeated Russian Nadia Petrova in last year's final to capture a third straight New Haven championship. Schiavone was this year's French Open runner-up to Li and captured the title at Roland Garros last year.

The start time for Saturday's final was moved up four hours to 1 p.m. (et) due to potential problems caused by Hurricane Irene.

The 2011 New Haven titlist will earn $103,000.