US plans to create a new Iraqi army have suffered a setback after hundreds of recruits resigned.
US plans to build up a 40,000-strong Iraqi army by next October
The army's first 700-man battalion lost 300 troops who were within weeks of being deployed, Pentagon officials say.
The battalion is the only one trained so far for what is eventually hopted to be a 40,000-strong force.
The US-led coalition in Iraq has played down the incident, saying it was just a dispute over pay and many more men were ready to join up.
However the BBC's Nick Childs at the Pentagon says the resignations will make for red faces in Washington.
This is a clear embarrassment for the Pentagon, given how much it has been trumpeting its advances in recruiting Iraqi security forces, our correspondent says.
While Pentagon officials say they will be looking into what is behind these departures and trying to address the problem, they are also playing down its significance.
They argue that, in a sense, rebuilding the Iraqi army is the least immediate security concern.
The threat, they say, is not from a conventional external enemy but from an insurgency - so the priorities are things like the police and the civil defence corps.
"We are aware that a third... has apparently resigned," Pentagon spokesman Lieutenant Colonel James Cassella said.
"We are looking into that in order to ensure that we can recruit and retain high-quality people for a new Iraqi army," he added.
The US says it is more important to recruit police officers
In Baghdad, a coalition spokesman Charles Heatley told the BBC that the incident was just a pay dispute.
"They used to be paid two dollars a month and now the recruits are being paid $60 a month, but they feel they ought to be paid more than that," he told the BBc World Service's Newshour programme.
"That's fine, if that's what they want, then they can go find another job. There are plenty of people queuing up to join the new Iraqi army."
Mr Heatley said those who resigned were demanding to be paid more than the police because soldiers are confined to barracks.
Washington places great importance on handing over security duties to Iraqis.
Some 130,000 US troops are in the country at the moment.
The new Iraqi army is being preparing for deployment primarily to guard borders and run checkpoints.
A second battalion is still in training.
In October, there was much praise from the US officials when the first battalion - which included 65 officers - completed a nine-week basic training course led by US instructors.
US administrator in Iraq Paul Bremer said the graduates were the core "of an army that will defend its country and not oppress it".
US Defence Secretary Donald Rumsfeld and other Pentagon officials have repeatedly trumpeted the growth of Iraqi security forces - saying it was being formed with an amazing speed.
"Across the country, Iraqi security forces - now numbering close to 160,000 - are assuming responsibility for the security of their country, " Mr Rumsfeld said on Tuesday.