Reigning world indoor 400m gold medallist Debbie Dunn has withdrawn from the US world outdoor championship team with an unspecified injury, USA Track & Field (USATF) said on Monday.

USATF spokeswoman Jill Geer said she had no additional information on the injury and neither Dunn nor her agent could be reached for comment.

The announcement came as the United States finalized its team for the August 27-September 4 world championships in Daegu, South Korea.

Former US 100 metres champion Mike Rodgers remained on the team pending a hearing on his positive test for a stimulant, officials said.

The fourth-fastest sprinter in the world this year, he was selected in the 100 metres and 4x100 relay.

Rodgers's agent told Reuters on Saturday the sprinter had tested positive for the stimulant methylhexaneamine after mistakenly consuming an energy drink that contained the banned substance.

His second or "B'' sample is scheduled for testing on Wednesday.

An arbitration panel will determine his eligibility for the world championships.

Dunn, third in the US trials, had been named to the American squad in both the 400 metres and the 4x400 relay pool.

She won her world indoor title and helped the Americans win the 4x400 relay at Doha in 2010.

Dunn, 33, will be replaced in the 400 by US fourth-place finisher Jessica Beard, who was already in the relay pool.

Keshia Baker will be Dunn's replacement in the relay.

USATF also said injured women's steeplechaser Delilah DiCrescenzo had been replaced on the team by Stephanie Garcia. DiCrescenzo was third in the US trials.