Economists and analysts are trying to gauge the costs to the economy and consumers if the United States loses its solid-gold credit rating — a move that appears more likely now that the standoff in Washington over government spending has calcified.

Some economists say the effects of lowering the federal government’s credit rating to AA from AAA can be measured in the billions of dollars in increased borrowing costs for the government, and in the billions more that consumers, corporations, states and municipalities will have to pay for their credit. It could also erode consumer and business confidence, slowing even further the economy and job creation.

The prospect of a downgrade by one of the credit rating agencies once seemed almost unimaginable. But the impasse in Washington over the government’s deficit and $14.3 trillion debt limit has led some global financial players to expect the change.

A downgrade on debt issued by the United States would have less severe consequences than a default, which takes places when a government fails to pay its creditors. Many Wall Street bankers on Tuesday said they still believed a default would be avoided because its consequences for the markets and economy could be catastrophic. They were less certain, however, what the cumulative effect might be of a downgrade.