Berlin  - Defending champion Brad Walker pulled out of the men's pole vault at the world championships shortly ahead of the qualifying round on Thursday due to hip problems.

United States team officials said that Walker had not recovered in time from the injury which came at a recent meet in Monaco when he landed half on the mat and half on the ground.

Walker won worlds gold in 2007 and silver in 2005 and was the sixth best vaulter this year with 5.80m. The withdrawal in Berlin is his second straight disappointment on the big stage after managing no height in qualifying at the Olympics last year.

Olympic champion Steve Hooker of Australia was also an injury concern, but set to jump on Thursday. (dpa)