NEW YORK - Warren Buffett likens it to a nuclear attack. Economists warn that government spending on programs like Social Security would plunge. The Treasury says the economy would slide into a recession worse than the last.

Yet you wouldn't know that a U.S. debt default could amount to a nightmare from the way many companies and investors are preparing for it: They aren't. The assumption seems to be that in the end, Washington will find a way to avert a default.

"Doomsday is nigh, and everyone shrugs," said Nicholas Colas, chief market strategist at CovergEx Group, an investment brokerage in New York.

Brian Doe, a wealth adviser at Gratus Capital Management in Atlanta, has 35 clients who've entrusted him with $50 million for safekeeping. He isn't losing sleep over a potential default. Neither are his clients, apparently. Not one has called him about the issue, he said.

"I've not done anything," he said. He puts the odds of default very low. "People in Washington are stupid but not that stupid."

Marcello Ahn, a fund manager in Seoul, is more prepared, sort of. He doesn't think the U.S. will default. But if it does, the economically sensitive stocks of shipbuilders and chemical companies will get hit especially hard. So he's held off buying them.

But he hasn't sold a single stock or made any big moves to protect his portfolio.

"We are not taking actions based on the worst-case scenario," he said.

That worse case is inching closer. The Treasury says it will run out of money to pay its bills if Congress doesn't increase its borrowing authority by Thursday. That includes paying interest and principal on already issued U.S. Treasurys, considered the most secure financial bet in the world.

Treasurys are used as collateral in trillions of dollars of loans rolling over every day. They are also the standard against which the riskiness of stocks and bonds are measured. A default would cast doubt on the value of those assets and throw the global financial system into chaos.

Which is a key reason many seem unprepared for it: Why bother if you can't really protect yourself? Or, as an official response from France's Total oil company put it, "Nobody can imagine the consequences, so we don't have any plans."

Neither apparently does Sony Corp. "There isn't a whole lot that one company can actually do," CEO Kazuo Hirai said Friday at the company's Tokyo headquarters.

Still, the business world isn't entirely unprepared. Big U.S. companies have been hoarding cash since the financial crisis for fear of another credit crunch. And financial regulators, major banks and mutual funds have moved to shore up their defenses, too.

One area of concern is Treasury bills that mature shortly after Thursday. The fear is that owners of those bills may not get their money returned to them in case of a default.

As a result, the Hong Kong stock exchange is demanding that investors who use those bills as collateral in certain trades post more of them because they are riskier now. Funds that usually are filled with Treasury bills are scrambling to protect themselves, too. In a rare move, Fidelity Investments and JP Morgan Chase said last week they had purged their money market funds of all U.S. bills coming due soon after the default deadline.

Owners of U.S government bonds due later are less likely to get stiffed. But they're still vulnerable. In the event of a default, Standard and Poor's and other credit-rating agencies will consider those bonds higher risk and likely downgrade them. That could cause their prices to plummet, guaranteeing losses to sellers who can't wait until the bonds mature. But the specter of a downgrade has yet to scare many.

Insurer Allianz Group in Munich holds Treasurys in its portfolios to maturity, so a downgrade would have no effect on the company, spokesman Michael Matern said.

Another area of concern is what Wall Street calls "liquidity" - the ability to access cash quickly to pay lenders and suppliers. Many companies have assets they could sell to scare up money in a pinch. But any panic in markets after a U.S. default would make it difficult to find buyers just when they are needed most. Buyers fled after the collapse of Lehman Brothers five years ago, turning a bankruptcy into a financial crisis and plunging economies around the world into recession.