A day of catastrophic financial reckoning is coming for the United States and we're not prepared for it, says former Secretary of the Treasury Paul O'Neil, who served in the first George W. Bush administration.

"This (current) financial crisis in retrospect will look like a child's game compared to what we're headed into when we have to begin raising enormous amounts of money through floating debt," said O'Neil in a recent interview on PBS.

The United States will either have to raise immense amounts of cash or renege on our Social Security and Medicare benefits obligations," O'Neil said. Possibly, both, say some observers.

Our impending financial calamity, O'Neil points out, "... is $53 trillion (that's trillion) worth of unfunded liabilities that we, the American people, have signed up for. Most of the American people don't know that we have these so-called unfunded liabilities."

When those bank-busting bills start coming due, who will keep lending us money, O'Neil asks.

"Nations around the world ... are going to have better places to invest their money than the United States because the currencies will be more sound than ours and the inflation rates will be lower," said O'Neil

"We've sowed the seeds of our own undoing unless we take some action," he warned.

Those seeds may have already taken root. A late March auction of U.S. government debt failed to attract strong demand, The Wall Street Journal reported. The tepid response may indicate growing doubts about the economy and the strength of the U.S. dollar.