WASHINGTON — The deficit in the broadest measure of U.S. trade fell in the July-September quarter to $100.6 billion, the smallest imbalance in three years.

The current account trade imbalance declined by 19.2 percent from a second quarter deficit of $124.4 billion, the Commerce Department reported Tuesday. The improvement reflected a smaller deficit in goods trade, a bigger surplus in services such as financial services and a bigger surplus in income from overseas investments.

The current account is the most complete measure of trade because it includes not only goods and services but investment flows and other payments between the United States and the world.

President Donald Trump has promised to reduce America’s trade deficit by attacking unfair foreign trade practices, which he says have cost millions of American factory jobs.

The third quarter deficit represented 2.1 percent of the total economy, down from 2.6 percent in the second quarter. It was the smallest deficit in dollar terms since a current account imbalance of $91.9 billion in the third quarter of 2014.

The smaller deficit in goods reflected gains in exports of manufactured goods, which have been helped this year by a weaker dollar. That makes U.S. products cheaper on foreign markets. The third quarter gain was led by increases in sales of commercial aircraft, including engines and airplane parts, and increased shipments of telecommunications equipment.

Trump views America’s trade deficits as a sign of economic weakness. He blames them on bad trade deals and abusive practices by China and other trade partners.

But many economists believe the deficits are not caused by flawed trade agreements or cheating by particular countries, but by economic fact of life that Americans spend more than they produce and imports are needed to fill that gap.