The Pentagon warned its workforce on Monday that it is preparing for a possible government shutdown if Congress fails to break a political impasse.
If US government agencies are forced to shutter, American troops around the world would stay on the job and some civilian employees would be ordered on unpaid leave, Pentagon spokesman George Little told reporters.
But paychecks for military service members might be delayed while Congress would have to take action to ensure retroactive pay for civilians required to come to work, he added.
"Military personnel would be paid but maybe not on time," he said.
Defense Secretary Chuck Hagel planned to send out a memo to department workers Monday saying the Office of Management and Budget had asked the Pentagon "to review and update our plans in order to prepare for an orderly government shutdown," according to Little.
President Barack Obama's administration believes that Congress should find a political agreement to avoid "a lapse in funding," he said.
"A shutdown would put severe hardships on an already stressed workforce and is totally unnecessary," he added.
A deeply divided Congress has until October 1, the beginning of fiscal year 2014, to reach a budget compromise.
House Republicans voted Friday for a spending plan that strips all funds for Obama's health care law, setting up a confrontation with the Democratic-led Senate, which is expected to reject the measure.
The Pentagon did not say what share of its civilian employees would be furloughed if the shutdown goes ahead next week.
Military operations in Afghanistan would not be affected by a shutdown and would continue, Little said.
"We're going to continue the war effort."
When the Pentagon prepared for a possible shutdown in 2011 that was averted in a last-minute deal, officials designated certain department activities as necessary that needed to continue.
The "essential" services included medical care, mess halls, child care, legal offices, logistics, training, department schools and some accounting sections.