The rate at which debt in the United States is growing is unsustainable, and the only way to battle it is with a two-pronged approach, Republican Sen. James Lankford told CNBC on Thursday.
"If we don't have economic growth and if we don't limit our spending, then we will never get on top of the debt and deficit issues," he told "Squawk Box."
The national debt is just under $20 trillion. The deficit for fiscal year 2016, which ended on Sept. 30, rose to $587 billion, or 3.2 percent of the nation's gross domestic product.
Lankford said interest rate hikes could enlarge the debt even while being a sign of economic growth.
"When interest rates tick up, and you and I both know that interest rates will tick up, in the next eight years it's forecast we'll spend more on interest on our debt than we do on national defense. That is not long-term sustainable for us," the Oklahoma senator said.
"The reason we can't do more on highway funds, the reason we can't do more on so many areas, is because the first payment is always to [pay] our interest," he added.
And, when interest on the debt goes up and requires larger payments, the country will lose the ability to invest in other, much-needed areas and fall into a perpetual, debilitating economic cycle, Lankford said.
"It's as if I'm paying my grandparents' minimum payments on their credit cards, my parents' minimum payments on their credit cards and my minimum payments on credit cards. At some point, you don't have enough discretionary income to do everything else," he said.
The Treasury Department calculated the U.S. interest expense since fiscal year 2017 began Oct. 1 already to be more than $23 billion — $23,043,294,709.73 to be exact.
Clarification: This story was revised to clarify that the more than $23 billion in interest expense was since Oct. 1.