DAEGU (Yonhap) -- South Korean female pole vaulter Choi Yun-hee tied her own national record in the qualification round at the World Championships in Athletics Sunday, but that still wasn't enough to put her in the final.

Choi cleared 4.40 meters in her first try to tie the national mark, but failed in all three of her attempts to reach over 4.50 meters.

The 25-year-old needed to clear 4.50 ｍeters in her first chance to qualify as one of 12 finalists. She later lamented that she should've been able to get over that hump.

"I had placed the bar at 4.55 ｍeters in practices and I had a lot of confidence going in," Choi said. She had set the Korean record two months ago.

She said she switched to a heavier pole before her third crack at 4.50 meters, trying to draw back on some positive memories.

"In practice, I did well with the heavy pole and easily cleared 4.50 meters," Choi said. "It just wasn't working today."

She bristled at the suggestion that tying the national record should rate as a good performance.

"I clear 4.40 meters all the time," Choi said. "When I clear that height on the first try, I could tell vaulters ranked below me panicked. If I can handle the heavier pole better, I should easily be able to jump 4.50 meters."

Choi said the disappointment here isn't the end of the world, with the London Olympics only about a year away.

"I will try to make a lot of technical improvements," she said.

"I will try to make sure I put down my pole from a higher angle and give myself a higher trajectory."

Yelena Isinbayeva, world record holder from Russia, was among the dozen qualifiers, along with American Jennifer Suhr, who owns the top record in 2011 at 4.91 meters. (Yonhap News)