WASHINGTON — Consumer spending, the critical bulwark that has kept the country out of recession, is showing signs of cracking. Retail sales plunged by 0.4 percent last month as consumers handed retailers their worst Christmas in five years. Consumers have been battered by a sinking housing market, rising unemployment and the credit crunch.

The Commerce Department's sales report yesterday was just the latest in a string of weaker-than-expected numbers that have economists worried that the current economic expansion, now in its seventh year, could be in danger of faltering.

Analysts said the worry is that all the problems weighing on the economy could prompt consumers — who account for two-thirds of economic activity — to sharply limit or even stop shopping. Already, consumer confidence has slipped significantly amid the oil price spiral and the continuing housing slump. At the same time, some of the nation's biggest financial institutions have reported billions of dollars in losses stemming from a meltdown in the mortgage market.

"There is certainly enough out there to make people worry," said David Wyss, chief economist at Standard & Poor's in New York. "We think we are getting very close to a recession."

That view was echoed by former Federal Reserve Chairman Alan Greenspan, who said the country may already be in a downturn. "The symptoms are clearly there," he said in a Wall Street Journal interview yesterday. "Recessions don't happen smoothly. They are usually signaled by a discontinuity in the market place and the data of recent weeks could very well be characterized in that manner."

Stock prices, one of the leading indicators used to judge the course of the economy, continued their 2008 swoon.

The Dow Jones industrial average fell 277.04 points to close at 12,501.11, the lowest close in nine months. Investors were rattled by an announcement from Citigroup Inc. that it had sustained a $10 billion loss in the fourth quarter, reflecting in part the souring mortgage market.

Even before the problems with December retail sales, businesses were seeing inventories rise, including a 0.4 percent increase in November. An unwanted rise in inventories can translate into future production cutbacks by factories. A key gauge of manufacturing activity gave a recession reading earlier this month, falling to its lowest level in five years. In other news yesterday, the Labor Department said wholesale inflation, which had shot up in November by 3.2 percent, the largest amount in 34 years, dipped by 0.1 percent in December. That reflected a big drop in energy costs at the time. However, for all of 2007, wholesale prices rose by 6.3 percent, the biggest annual increase in 26 years.

Analysts said the dip in wholesale prices for December, if followed by a benign report today on consumer prices, should give the Federal Reserve the leeway it needs to more aggressively attack the economic slowdown with interest rate cuts.