The nation can't rely on taxes and spending cuts to get the problem under control, Fink wrote in his annual letter Tuesday. He raised the prospect of a "bad scenario" akin to Japan's economy in the late 1990s and early 2000s, which led to a period of austerity and stagnation.

"A high-debt America would also be one where it's much harder to fight inflation since monetary policymakers could not raise rates without dramatically adding to an already unsustainable debt-servicing bill," said Fink, 71.