The US Defense Secretary Chuck Hagel sounded an alarm bell on Saturday about budget cuts he said threaten US security and global military role, while "gambling" over the risk of an unexpected threat.
The cuts, which amount to nearly $1 trillion for the Department of Defense over a decade, were "too steep, too deep and too abrupt," Hagel told a defense conference in California.
"This is an irresponsible way to govern, and it forces the department into a very bad set of choices."
Automatic cuts of $52 billion set to take place in fiscal 2014 represent 10 percent of the Pentagon budget.
The Navy's global presence is already down 10 percent since sequestration began in March, while the army has canceled training rotations for 15 percent of its forces.
"The effects will be felt for a long period of time to come. By continuing to cancel training for non-deploying personnel, we will create a backlog of training requirements that could take years to recover from," Hagel said.
The defense chief was speaking at the Ronald Reagan Defense Forum, a one-day event hosted at the late US leader's presidential library northwest of Los Angeles.
The Pentagon has made clear to Congress and the White House "the growing difficulties we face in training, equipping and preparing our forces under a cloud of budget restraints and uncertainty," Hagel said.
"These challenges are often not visible, but they are very very real, and they will become more visible as they further jeopardize the security of our country as our readiness, capability and capacity continue to deteriorate."
The budget crisis comes as the US military is drawing back after more than a decade of war in Iraq and Afghanistan following the September 11, 2011 attacks.
The sequester was devised as a poison-pill austerity program in 2012, with mandatory cuts spread over 10 years aiming to force battling Republicans and Democrats to compromise on a long-term program to reduce the country's deficit.