WASHINGTON — The U.S. economy grew at a 6.6% annual rate last quarter, slightly faster than previously estimated, the government said today in a report that pointed to a sustained consumer-led rebound from the pandemic recession. But worries are growing that the delta variant of the coronavirus is beginning to cause a slowdown.

The report from the Commerce Department estimated that the nation’s gross domestic product — its total output of goods and services — accelerated slightly in the April-June quarter from the 6.5% it had reported last month. The economy’s expansion last quarter followed a solid 6.3% annual growth rate in the January-March quarter.

In recent weeks, though, many economists have been downgrading their estimates of GDP growth for this quarter, and for 2021 as a whole, as the now-dominant delta variant has sent confirmed COVID-19 cases rising throughout the country.

New reported cases are now topping 150,000 per day, the highest level since late January. As a consequence, real-time tracking of consumer activities, notably for airline travel and restaurant dining, has weakened in recent weeks.

Goldman Sachs has cut its forecast for annual growth in the current July-September quarter from 9% to 5.5%, citing the effects of the delta variant. Likewise, Wells Fargo economists have downgraded their third quarter GDP forecast from an 8.8% annual rate to 6.8%, also because of the surge in COVID cases.