The economy lost 17,000 jobs in January, the Labor Department reported on Friday, the first monthly decline in four years and the most striking evidence yet that the United States may be slipping into a recession.

Until now, the labor market had been growing at a steady if softening pace. Many economists pointed to expanding payrolls as the final holdout in a sluggish economy weighed down by trouble on Wall Street, the collapse of the housing bubble, and a cascade of credit problems linked to soured subprime mortgages.

But the January employment report cast the job market in a startlingly darker light. Jobs disappeared across a broad spectrum of professions, with the steepest losses coming in the manufacturing, construction and goods-producing industries.

Adding to the gloom, the government said that the level of employment was sharply lower in December than it had originally estimated. The new figure was based on an annual review of every job covered by unemployment insurance.