(CNN) -- The national debt is bad for the military, Joint Chiefs of Staff Chairman Adm. Michael Mullen is telling business men and women and others on a three-day "Conversations with the Country" tour across the Midwest.
Mullen's trip, which ends Friday in Cleveland, Ohio, is aimed at encouraging business owners to hire veterans.
"The most significant threat to our national security is our debt," he told CNN Wednesday. "And the reason I say that is because the ability for our country to resource our military -- and I have a pretty good feeling and understanding about what our national security requirements are -- is going to be directly proportional -- over time, not next year or the year after, but over time -- to help our economy.
"That's why it's so important that the economy move in the right direction, because the strength and the support and the resources that our military uses are directly related to the health of our economy over time."
The wars on Iraq and Afghanistan have contributed to a more than doubling of the Pentagon budget, which has jumped from $300 billion to $664 billion since 2000.
Defense Secretary Robert Gates has called on his department to find $100 billion in overhead savings over the next five years. Speaking Thursday to the Economy Club in Detroit, Michigan, Mullen agreed that the Pentagon needs to "cut the fat."
"We're not a business," he said in Detroit. "Part of us does this really well. Parts of us have never had to, plus our budget has doubled over the last 10 years."
The admiral said the Pentagon has not been as proactive as it should have been in prioritizing spending and said the department must adopt responsible fiscal practices.
"A lot of those skills have to be sharpened," Mullen said.
Both industry and the military need to hone those skills, he said, to avoid "this wave of debt."
"It's the responsibility of both sides," he said. "We have to gird ourselves for some pretty significant challenges, given the national security challenges that we have as well as the responsibility to steward every dollar that we have."
Mullen has been telling his audiences that interest on the debt will nearly equal the defense budget in two years, but Congressional Budget Office numbers, in a report released in January, show the interest payment approaching the Pentagon's 2000 budget in 2012 and reaching its 2010 budget in 2019.