Worries about North Korea and terrorism aside, Sen. Bob Corker said Thursday "our biggest threat is ourselves."
Corker told CNBC his top concerns are passing a health-care bill and avoiding an "almost inevitable" fiscal disaster.
"We have $20 trillion in debt and we're continuing to do things that make that worse every day," Corker said on "Squawk Box." "And I believe unless something abruptly changes very soon, we will have a fiscal calamity, and it's going to make all the other ills that we're dealing with in the nation pale."
Lawmakers will meet again on Monday after their Fourth of July break. A top priority is dealing with the Republicans' attempt to repeal and replace the Affordable Care Act.
Corker blames some states that are concerned with Medicaid cuts outlined in the bill as "holding us hostage" from ever being able to pass a bill.
On the numbers side, Corker said spending would increase but the revenues would decrease, thus moving further away from balancing the budgets and "hastening the fiscal demise."
He said all of the Obamacare tax revenues, about $750 billion, would be eliminated under the Senate GOP health-care plan.
"So not only are we beginning to spend more money on the Medicaid side — and now we're getting ready to flood the zone with opioid treatments," he said. "Now $750 billion will be coming out of the revenue side. So not only are we spending more here, we're reducing the amount of revenues that are coming in."
Corker said the only way to pass the Senate bill — and avoid an impending financial crisis — is through realistic, specific compromise.
"We're the greatest nation on Earth, we just need to make sure that we keep ourselves that way," he said.