|Denmark's Rikke Moller Pedersen swims in the women's 200m breaststroke heats during the World Swimming Championships at the Sant Jordi arena in Barcelona August 1, 2013. REUTERS/Michael Dalder (SPAIN - Tags: SPORT SWIMMING)|
Pedersen, 24, clocked two minutes 19.11 seconds to beat the previous mark of 2:19.59 set by American Rebecca Soni at the Olympic Games in London last year.
The Dane, whose previous best was 2:20.53, finished fourth in London and was seventh at the last world championships in Shanghai two years ago.
"It was very fast," Pedersen said in an interview with television broadcaster Eurosport.
"I am really happy with the personal best and I really hope I can improve in the final (on Friday)."
(Reporting by Iain Rogers; Editing by John Mehaffey)