Defense Secretary Leon Panetta on Thursday ordered the US military to "prepare for the worst" and take cost-saving measures as it faces the threat of potential deep budget cuts.

The steps include scaling back maintenance, freezing civilian hiring and delaying some weapons contracts, Panetta told a news conference.

The US military's vast budget is the by far the largest in the world, with proposed spending for fiscal year 2013 of roughly $614 billion, and will remain so -- despite what Panette dubbed a "perfect storm of budget uncertainty."

"We have no idea what the hell is going to happen," he added. "All told, this uncertainty, if left unresolved by the Congress, will seriously harm our military readiness."

The uncertainty stems from Congress's failure to adopt a defense budget for the current fiscal year 2013, its inability to resolve a stalemate that could trigger massive cuts and a looming crisis over the country's debt ceiling.

If lawmakers fail to approve the Pentagon's proposed budget for 2013, the department will suffer an $11 billion cutback to funding for operations and maintenance, he said.

If Congress cannot agree on a deal to stop automatic budget cuts, known as "sequestration," by March 1, the Defense Department would see funding slashed by more than $50 billion this year and $500 billion over ten years.

As a result, Panetta said: "We really have no choice but to prepare for the worst."

The announcement marked the first concrete measures by the Pentagon's leadership to prepare for cuts.

Panetta, who is due to retire soon after President Barack Obama nominated ex-senator Chuck Hagel as his successor, said the precautionary steps he had ordered should be "reversible," in case lawmakers clinch an agreement.

But he did not say how much the measures would save.

If the sweeping budget cuts come to pass, the military would seek to shield troops deployed to Afghanistan from the effect of the reductions, Panetta said.

That would mean "very serious cutbacks" for other training, scaling back flying hours for pilots and time at sea for ships as well as disruptions to most weapons programs, he said.

In addition, the entire civilian workforce for the Defense Department would be subject to furloughs and the cost-saving measures would harm the military's readiness, he admitted.

The chairman of the US Joint Chiefs, General Martin Dempsey, was even more blunt about the possible impact of automatic budgets cuts.

Although troops on the battlefield and wounded soldiers would be safeguarded from any budget cuts, the rest of the armed forces would be hit hard, the general told the same press conference.

"We won't short-change those in combat, and we'll continue to resource those who are the next to deploy," Dempsey said.

"But for the rest of the force, operations, maintenance, and training will be gutted. We will ground aircraft, return ships to port, and sharply curtail training across the force."

Dempsey, painting a dire scenario, said the military's "readiness will begin to erode" and warned: "Within months we will be less prepared, and within a year we will be unprepared."