Li Na of China returns the ball to Kateryna Bondarenko of Ukraine in the first round of the U.S. Open tennis tournament in New York, Tuesday, Aug. 31, 2010. Bondarenko upset eighth-seeded Li 2-6, 6-4, 6-2. [Xinhua/Shen Hong]

Ukraine's Kateryna Bondarenko staged the first major upset of the US Open on Tuesday by ousting Chinese eighth seed Li Na 2-6, 6-4, 6-2.

Li, Asia's top-ranked player, also the highest Chinese seed in Grand Slam history, made her best Slam run into this year's Australian Open semi-finals and entered the year's last major tournament with a Chinese best-ever world number nine ranking.

But in heat of 96 degrees Fahrenheit that scorched down on Louis Armstrong Court, Li struggled to unforced errors after breezing through the first set in only 31 minutes.

Li's early exit came much from her own rather than from her opponent. She committed 45 unforced errors, 19 more than her Ukraine rival, rendering an lop-sided deciding set to Bondarenko.

Though Li complained over scorching weather after the match, but it's evident the emotional factors functioned catalyst in her quick sliding in the second and third sets.

"It was so hot," Li said. "I felt good in the first set. The second set, I felt like I died. The energy just faded."

Li struggled against lethargy in the second set, but just could not shrug off the rallying efforts from Bondarenko, who came to be energetic and thriving in the second set.

The second set loss propelled Li's to diminish composure and sped up her early exit.

It was the first opening-round exit for Li at a Grand Slam event since the 2006 Australian Open. Her only other round one Slam loss was in her 2005 US Open debut.