Testifying before the House Appropriations defense subcommittee, the five uniformed leaders of the military branches described how national security would be put at risk if they are forced to make deep decreases in spending for personnel, training, and equipment modernization programs.

Their appearance marks the fourth time in the last three weeks that top Pentagon's leaders have testified before a congressional oversight committee about how the country's fiscal outlook affects the armed forces. Their warnings of a looming readiness crisis haven't changed, but the pending deadline has made them more urgent.

"If we do not have the resources to train and equip the force, our young men and women will pay the price, potentially with their lives," said Gen. Ray Odierno, the Army chief of staff.

Despite the dire predictions, many of the cuts to hit the Defense Department and other federal agencies would come in later years and could be partially offset by cuts in programs that are wasteful or behind schedule. Rep. Duncan Hunter, R-Calif., criticized Defense Department officials earlier this month for "adding drama" to the sequestration debate by publicly highlighting the cuts to readiness accounts.

The automatic cuts, known as a sequester in Washington speak, are scheduled to begin on March 1 and are the result of Congress' failure to trim the deficit by $1.2 trillion over a decade. The Pentagon faces a $46 billion budget reduction through the end of September, and additional cuts would come in future years as long as the sequester remains in effect. The military also has to absorb a $487 billion reduction in defense spending over the next 10 years mandated by the Budget Control Act passed in 2011.

The military's fiscal challenges are further complicated by the lack of a budget for the current fiscal year. Congress hasn't approved one. Instead, lawmakers have been passing bills called continuing resolutions, which keep spending levels at last year's rates. That means the Pentagon is operating on less money than planned, compounding the financial problem facing the armed forces, defense officials said.

Gen. James Amos, the Marine Corps commandant, said the sequester combined with the lack of a 2013 defense budget will have a "devastating impact" on military readiness and create "unacceptable levels of risk" to the U.S. national security strategy.

Amos said America's allies and enemies are watching to determine whether the country remains able to meet its commitments overseas. "Sequestration viewed solely as a budget issue would be a grave mistake," he said.

Gen. Mark Welsh, the Air Force chief of staff, said the sequester and the failure to pass a 2013 budget will "combine to render us unable to continue our current and expected level of operations."

The Pentagon has previously announced that it is cutting the U.S. aircraft carrier presence in the Persian Gulf region from two carriers to one, and Adm. Jonathan Greenert highlighted that move as one of the most significant effects of the sequester.

Greenert, the chief of naval operations, also said that if a 2013 budget isn't passed, the Navy will have to stop the refueling overhauls to two other carriers - the USS Abraham Lincoln and the USS Theodore Roosevelt - and delay the construction of other ships.