The number of people signing up for unemployment assistance in the United States rose 28,000 last week to a total of 385,000.
Thursday's report from the Labor Department is the worst since November, and is higher than most economists predicted.
Initial claims for unemployment benefits are a way of tracking how many workers have been laid off recently. The latest report runs counter to a trend of improving readings since jobless claims hit a peak in 2009 during the financial crisis.
Friday, government experts will take a more detailed look at the U.S. job market when they publish the unemployment rate for March. Economists surveyed by the Bloomberg financial news service predict the unemployment rate will stay at a relatively high 7.7 percent.
They also predict that the U.S. economy gained 195,000 more jobs than it lost, as some companies falter and other firms take their places. The gain in February had been higher at 236,000 jobs.