WASHINGTON – Americans took on more debt in May and used their credit cards more for only the second time in nearly three years. Consumers stepped up their borrowing just as the economy began to slump and hiring slowed.

The Federal Reserve said Friday that consumer borrowing rose $5.1 billion in May, the eighth straight monthly increase. It followed a revised gain of $5.7 billion in April. Borrowing in the category that covers credit cards increased, as did borrowing in the category for auto and student loans.

The overall increase pushed consumer borrowing to a seasonally adjusted annual level of $2.43 trillion in May. That was just 1.7 percent higher than the nearly four-year low of $2.39 trillion hit in September.

Borrowing is a sign of confidence in the economy. Consumers tend to take on more debt when they feel wealthier. That boosts consumer spending which gives businesses more faith to expand and hire.

But an increase in credit card debt can also be a sign of people falling on harder times.

The economy added just 18,000 jobs in June, the fewest in nine months and the second straight month of feeble job growth. The unemployment rate rose to 9.2 percent, the highest of the year.

The increase in credit card borrowing marked only the second monthly gain since August 2008. Households began borrowing less and saving more when unemployment spiked during the Great Recession.

Many have resisted using credit cards in the two years since the downturn ended. Even with the May increase, this category is down 4.4 percent over the past year and 18.5 percent from its peak in August 2008.