The Pentagon says the temporary budget resolution that took effect Monday fails to authorize the U.S. military to continue training Iraqi security forces.
Congress did not include the Iraqi Security Forces Fund in the short-term spending measure it passed last month to fund the government.
Defense officials say none of the military trainers will be called back to the U.S. immediately while the Pentagon works through the issue.
Officials say there are fewer than 200 U.S. troops in Iraq, and fewer than 100 other Defense Department civilians and contractors. They say the Pentagon is exploring ways to possibly continue the training.
The U.S. Embassy's police training program has been touted as a key effort to continue supporting Iraqi security forces after the American military withdrew from Iraq last year.