Officials also slashed growth for last year using newly available data -- cutting a crucial 2018 GDP measure to 2.5 percent, undercutting President Donald Trump's frequent boasts about beating 3.0 percent.
The new data covering the past five years now show the world's largest economy actually slowed in the year after Trump pushed through a sweeping tax overhaul.
The updated data also highlight how momentum deteriorated in the final months of 2018, when the Federal Reserve raised interest rates in defiance of intense pressure from Trump.
The central bank next week is widely expected to cut its benchmark lending rate, reversing December's increase.
The Commerce Department reported that GDP in the April-June quarter slowed to 2.1 percent from the first three months of the year, slowing sharply from 3.1 percent growth in the first quarter, but that was better than expected, helped by strong consumer spending.
Taken together the new data portrayed an economy that enjoys robust strength in some quarters but has begun to sputter worryingly in others, even while the US is outshining sluggish economies in Europe, Japan and elsewhere.
Analysts had expected second quarter growth of just 1.8 percent, but the economy got a boost from strong consumer spending on autos, food and clothing.
Federal spending also took its biggest leap in a decade -- with non-defense spending rising at the fastest pace in 21 years -- a one-time jolt when the government resumed paying employees following the five-week partial government shutdown at the start of the year.
But that was not enough to make up for tumbling investment in factories and commercial buildings, which sank more than 10 percent for the quarter, and falling income from software royalties and other intellectual property.
- A banner number no more -
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Amid a global economic slowdown, weakening foreign demand for US exports meant American factories sold fewer autos, parts and factory equipment.
The ailing American manufacturing sector also produced fewer non-durable goods while retail and wholesale trade softened.
Declining travel exports, dominated by tourists and foreign students, also weighed growth down for the quarter.
In the revisions that stretch back to the final quarter of 2013, the Commerce Department said revised and newly available data showed October-December 2018 was much weaker than previously reported, notably spending on healthcare and autos.
The fourth quarter of 2018 expanded just 1.1 percent, down from the 2.2 percent reported in March.
As a result, growth between the fourth quarter of 2018 and the fourth quarter of 2017 -- the measure of annual growth favored by the White House and many economists -- was chopped down to 2.5 percent from 3.0 percent.
Economists say comparing the fourth quarter to fourth quarter of the prior year gives a more accurate picture of the economy.
The downward revision stripped Trump of the banner 3.0 percent number he had repeatedly hailed on in public appearances and social media as the greatest economic performance in 14 years.
In policy documents, the White House claims the president's economic agenda of tax cuts, slashed regulation and trade reform will push the US economy to three percent annual growth over a decade.
Instead, the economy actually slowed following the tax cuts from 2.8 percent in 2017.