He said some businesses had already begun giving workers their layoff notices, and the issue would become more acute toward the end of the fiscal year in September.

“That kind of instability and uncertainty is what is going to drive us hopefully to finding a path, if not to a full solution ... at least to take some steps down the path of avoiding that train wreck,” Levin said.

The senator said he expected any deal to resolve the budget impasse would probably require some additional reductions in defense spending over the next decade

“My best guess is it would be about $10 billion more a year, tops, which would be $100 billion over a 10-year period,” Levin said.

He said raising revenues would have to be part of the solution, despite Republican resistance. He said government revenues historically had been about 19 percent to 20 percent of gross domestic product but had now fallen to about 15 percent.

“Every president that has achieved significant deficit reduction has made revenue part of the equation,” Levin said.