LONDON (AFP) - Olympic champions He Kexin of China and North Korea's Hong Un-Jong made their push for gold at the world gymnastics championships here on Wednesday.

He, the gold medallist in Beijing in the uneven bars, topped qualification with 15.975 points ahead of promising American talent Rebecca Bross (15.050) and North Korea's Cha Hong Gwa (15.025).

Hong, gold medallist in the pommel horse at the Olympics, was second after qualifying with 14.787, just behind Kayla Williams of the USA with 14.812.

Bross and Romania's Ana Porgras demonstrated their young talents by dominating the all-around event.

Bross, just 16, topped the charts with 57.400pts while Porgras scored 57.300. Australia's Lauren Mitchell was third (56.675) with China's Deng Linlin (56.350) in fourth.

Porgras, who has yet to celebrate her 16th birthday, wowed the crowds with her subtle and athletic routine, especially on the beam where she finished on top of qualifying.

"She is a fine gymnast, expressive and blessed with many talents," said Romania coach Nicolae Forminte. "I'm happy to see that she hasn't felt the pressure."

Britain's Beth Tweddle blew her chance of a medal on the uneven bars but the 2007 world champion did secure a place in the floor final.

Tweddle slipped during her uneven bar performance while trying to execute the 'Tweddle' - the move named after her.

She finished the routine but could only score 13.850 which left her out of the top-eight qualifying positions in 11th.

"I'm pretty gutted. I didn't know anything about it until I hit the floor," she said.