The plan is to transfer up to a brigade, or about 5000 soldiers, to the training role, they were quoted as saying by the New York Times, adding that many more would be assigned adviser jobs.
To compensate for the loss of fighting power, one officer said, commanders intend to put the Iraqi units they train in the field.
"It will be a process of 'train-fight-train'," the officer said.
Sunday's elections for a national assembly in Iraq have led to calls from some US lawmakers for an exit strategy for their troops, who first occupied Iraq in March 2003.
Both the White House and the Iraqi interim government have ruled out an immediate pullout, but Iraqi interim President Ghazi al-Yawir said on Tuesday US forces could start to leave by the end of the year.
There are about 170,000 foreign troops in Iraq, about 150,000 from the US alone, which led the March 2003 invasion to oust Saddam Hussein.