Looming budget cuts that will hit the US Defense Department from Friday will endanger the military's ability to conduct its missions, Pentagon chief Chuck Hagel warned.
"Let me make it clear that this uncertainty puts at risk our ability to effectively fulfill all of our missions," said Hagel, whose agency's budget is set to be slashed by roughly $46 billion.
In contrast with his predecessor Leon Panetta, who branded the cuts a "doomsday mechanism" and "fiscal castration," Hagel was more measured two days after taking office as defense secretary.
But he made clear what he thought would be the consequences of the so-called "sequester" on the military.
Defense officials say they will be forced to reduce the working week of 800,000 civilian employees, scale back flight hours of warplanes and postpone some equipment maintenance.
The deployment of a second aircraft carrier to the Gulf has also been canceled.
The US Navy will gradually stand down several hundred planes starting in April, the Air Force will curtail flying hours and the Army will cut back training for all units except those deploying to Afghanistan.
"This will have a major impact on training and readiness," Hagel said. "Later this month, we intend to issue preliminary notifications to thousands of civilian employees who will be furloughed."
Hagel acknowledged that the budget cuts "will cause pain, particularly among our civilian workforce and their families."
"I'm also concerned, as we all are, about the impact on readiness that these cuts will have across our force," he added.
But he expressed "confidence" that the White House and President Barack Obama's Republican foes in Congress would eventually reach a consensus.
Obama was bound by law to initiate the automatic, indiscriminate cuts, which could wound the already fragile economy, cost a million jobs and harm military readiness, by 11:59 pm (0459 GMT).
The hit to military and domestic spending, known as the sequester, was never supposed to happen, but was rather a device seen as so punishing that rival lawmakers would be forced to find a better compromise to cut the deficit.