WASHINGTON: A Republican plan to spare the Pentagon roughly $500 billion in spending cuts faces rough passage with no guarantee the department could avoid the spending reduction, two defense analysts say.

Sens. Kelly Ayotte, John McCain, Lindsey Graham, Joe Lieberman and John Kyl will roll out a “substitute” sequestration plan this week. Formal legislation will likely hit the Hill sometime in January, when Congress returns from the Christmas break, Ayotte said today. The freshman senator was light on details but she was clear the legislation would shift the $500 billion in spending cuts from the Pentagon’s budget and move them into other agencies budgets. Tough times demand tough decisions, Graham told reporters at the same event, but the times demand that “the first check you write should be for defense.”

However, the Obama administration has said it will veto any alternatives to the original sequestration plan. That threat may ultimately scuttle any plans to change the sequestration strategy, one top defense analyst said. The plan being worked by Ayotte’s group “does not answer the mail” according to Loren Thompson, a defense consultant and senior defense analyst at the Lexington Institute. While details are sparse, Thomson (a member of AOL-D’s board of contributors) says this alternate plan is basically dead on arrival because “it seeks to direct budget cuts away from Republican priorities rather than sharing the pain.”

“The devil [will be] in the details” Todd Harrison, a defense budget expert at the Center for Strategic and Budgetary Assessment, added. Finding spending cuts outside the Pentagon will force the group to either increase tax revenues, cut entitlement programs like Medicare or Social Security or adopt a slate of politically unpalatable options, Harrison said. And after all that, there is no guarantee that the Pentagon will be spared the budget ax, he added. Summing up the monumental task facing Ayotte’s group, Harrison said if there was a deficit reduction plan that could spare defense spending “the Super Committee would have come up with it”

The Pentagon faces the $500 billion budget cut because the congressional Super Committee failed last month to trim $1.2 billion from government coffers. That cut will be spread over the next 10 years beginning in fiscal 2013. The Pentagon is already building in a $450 billion spending cut passed by Congress this summer. Those cuts will also be spread across 10 years, beginning in fiscal 2012. The $450 to $500 billion in cuts already mandated, plus the $500 billion cut caused by the Super Committee’s failure, means the department is staring down a $1 trillion budget cut. Defense Secretary Leon Panetta and Former Chairman of the Joint Chiefs of Staff Adm. Mike Mullen have said that kind of cut would break the U.S. military. With this plan, Ayotte and her GOP colleagues hope to make sure that doesn’t happen.