At the Port of Los Angeles, the frenetic choreography of cranes unloading containers from Asia has slowed to a tiptoe and the noise at the busiest docks in the United States is quietening down.

"You could hear a pin drop, it's very unusual," port director Gene Seroka said.

By this unofficial barometer, the American economy faces a slowdown under President Donald Trump amid his trade war with China.

Along with the next-door Port of Long Beach, the area represents the biggest gateway in the United States for goods from China and the rest of Asia.

That has made it among the first victims to a burgeoning crisis threatening to disrupt the lives of millions of Americans.

Trump's on-again-off-again tariffs – and the retaliation launched by other countries – has cowed importers, whose usual orders for furniture, toys and clothing have dwindled.

For the week of May 4, the Port of Los Angeles will receive up to 35 percent less cargo compared with a year ago, Seroka said.

The Port of Long Beach says for the entire month of May it is expecting a 30 percent drop in imports.

Dozens of ships have cancelled their voyages to these ports.

"Many retailers and manufacturers alike have hit the pause button, stopping all shipments from China," said Seroka.

China is the hardest hit by Trump's tariffs, with levies as high as 145 percent on some goods. Sales of Chinese goods to the United Staes last year amounted to more than US$500 billion.

And while sales may not be going up this year, prices undoubtedly will.

"Effectively, the cost of a product made in China now is two and a half times more expensive than it was just last month," said Seroka.

That extra cost, which is paid by the importer of a product, not by the seller, will affect trade across the United States.

"This is not just a West Coast issue," warned Long Beach port director Mario Cordero.

"It affects every port, whether it's in the East or in the [Gulf of Mexico.

At the start of the year, Long Beach and Los Angeles saw American companies scurry to get ahead of tariffs that Trump promised on the campaign trail.

Cargo volumes surged as they tried to build up as much untaxed inventory as possible.

But as the tariffs begin to bite, they will undoubtedly hold buying to eat into that inventory.

Without a reversal from the White House that would re-open the trade spigot, that could mean shortages that consumers will start to notice, and soon, according to Seroka.

"American importers, especially in the retail sector, are telling me that they have about five to seven weeks of normal inventory on hand today," he said.

"If this trade dispute goes on for any length of time, we'll likely see fewer selections on store shelves and online buying platforms.

"The impact on American consumers will be less choice and higher prices," he said.

"The American consumer is going to get hit right in the wallet."

For Antonio Montalbo, one of the 900,000 logistics workers in Southern California, the ordeal has already begun.

As the owner of a small trucking company, he needs to replace the starter on one of his vehicles; the part, made in China, now costs twice as much.

Trump has "created a hostile environment at the port for the drivers," says the 37-year-old.

"We're angry at Donald Trump. He needs to go check out the country a little bit, because he has a lot of angry truck drivers.

"It seems like he doesn't care about the public or the working class."

Between skyrocketing maintenance costs and the fall-off in work, he estimates he could be laying off staff within six months.

Montalbo says he voted for Trump last November because he was fed up with inflation, and trusted him to fix the economy.

"I thought that he was a businessman.

"Now we have something worse than inflation, called tariffs." (AFP)