Carl Schuster, a former US Navy captain who spent 12 years at sea, explained to CNN that the close proximity of the two warships was of major concern.
The Chinese defense ministry said the Decatur's actions - and previous US sail-bys - threaten its sovereignty and security.
The U.S. accused China's navy of "unsafe and unprofessional" conduct near a Chinese occupied reef in the disputed South China Sea, in the latest show of tensions between the countries amid their escalating trade war.
In this October 13, 2016, photo provided by the U.S. Navy, guided-missile destroyer USS Decatur operates in the South China Sea as part of the Bonhomme Richard Expeditionary Strike Group. "Captains get very nervous when ships get closer than 1,000 yards (915 metres)", said Schuster, who now lectures at Hawaii Pacific University.
In a separate statement posted to China's Foreign Ministry website, spokeswoman Hua Chunying criticized the United States for "repeatedly resorting to provocative acts" and urged it to "immediately correct its mistakes".
In his annual address to the U.N. General Assembly, Trump said China's trade policies "cannot be tolerated" anymore.
A Chinese destroyer performed an "unsafe" maneuver during an encounter with a U.S. Navy warship in the disputed South China Sea over the weekend, coming within 40 meters (45 yards) of the American vessel's bow and forcing it to steer the ship away to prevent a collision, the U.S. military said Tuesday.
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China frequently challenges USA ships and aircraft passing through parts of the South China Sea, sometimes with radio warnings, but at other times by using harassing maneuvers.
Gorman said that the USA would "continue to fly, sail and operate anywhere global law allows".
However, the US disagrees with this version of events and claims a much more sinister meeting occurred, with US Navy officials calling the manoeuvre "unsafe and unprofessional".
American and Chinese warships have had close encounters in the past, he added, but Sunday's encounter "appears to have been closer than any recent event".
While the the notion of a shooting war between the United States and China may seem remote to casual observers, some market observers have noted the time honored progression of economic tensions like trade wars and currency wars eventually leading to a full-on hot war.
The U.S. had placed sanctions in 2017 on that exporter, Rosoboronexport, in response to Russia's interference in America's 2016 presidential election.
Those comments came after Trump accused China of meddling in the upcoming U.S. elections.
"They do not want me or us to win because I am the first president ever to challenge China on trade", Trump said.