WASHINGTON — The Federal Reserve is struggling to adapt to an economy that refuses to boom.

The Fed said on Wednesday, after a two-day meeting of its policy-making committee, that it would not raise its benchmark interest rate, and that future increases were most likely to unfold at a slower pace.

The seven-year period since the end of the Great Recession has become one of the longest economic expansions in American history and, at the same time, one of the most disappointing. The Fed, in a statement announcing its decision, noted what had become a typical mix of good news and bad.

Economic output has increased while job growth has slowed, the Fed said. Consumers are spending more while companies are making fewer investments. Exports are rebounding, but Britain’s June 23 referendum on whether to leave the European Union could set off another round of disruptions.

“Recent economic indicators have been mixed, suggesting that our cautious approach to adjusting monetary policy remains appropriate,” the Fed chairwoman, Janet L. Yellen, told a news conference.