“It's like a wrestling match: You have someone's foot to your throat and you can breathe, but only just enough,” Gonzalez said. “The border is the lifeline of our industry.”

The effects of Trump's threat are already being felt, tariffs or no. At the World Trade and Colombia Solidarity bridges, which carry about a total of 12,000 trucks across the border each day, wait times on Monday were higher than usual because of the increased orders to beat the tariffs.

Ernesto Gaytan, general manager and co-owner of trucker Super Transport International Ltd., said his company was running at full capacity last week. His entire fleet of about 500 vehicles was on the road moving goods across the border. One client quadrupled orders to save $18 million in potential tariff costs.

Storage spaces that filled up quickly last week to accommodate the influx are still packed because there aren't enough drivers, which meant Gaytan had to turn some clients away.

“We're still beyond full capacity,” Gaytan said Monday. “Everything gets impacted by the tariffs if they ever go in. Everything goes through Laredo. Everybody's going to feel the effects of it.”

Tariff Troubles in Texas

Texas, which accounts for more than a third of U.S. trade with Mexico, would be hardest hit by any tariffs on the country. About 117,000 Texas workers would lose their jobs if the full tariff went into effect, according to the Perryman Group. The state is second only to California in labor-market reliance on Mexican trade, data from the Wilson Center show. And 5.9 percent of the state's gross domestic product (GDP) is based on Mexican imports, second only to auto giant Michigan.

More than a third of U.S. imports from Mexico actually originated in America, with some items crossing the border multiple times. It underscores just how interconnected and complex the trading relationship is between the countries and makes it hard to quantify just how much Americans would be hit by the levies.

“When we're taxing things at the border, we're actually taxing U.S. goods,” said Katheryn Russ, an associate economics professor at the University of California-Davis. “Consumers may not notice, but it will filter down.”

Fruits and vegetables are among the top-traded commodities and the most time-sensitive. Rodolfo Delgado, who owns a 35,000-square-foot refrigerated warehouse in Laredo's north end, said his clients were worried delays at the border could hurt their produce.

“Importing fruits and vegetables, it's like importing a trailer of dynamite with a wick on it,” Delgado said. “You cannot hold it, you just have to send it to the final destination to be sold.”

Some of his clients were resigned last week to absorbing the 5 percent tariff hit, while others were opting to freeze their goods or looking at selling to Canada instead of the U.S., he said.

“There are many other countries in the world that will buy and sell to Mexico,” Delgado said Monday. “What we've got is the threat from Trump that's still looming on us, and people are really getting tired of it.”

With a final U.S.–Mexico trade deal still to be worked out, there's more unease hanging over the region.

“It's just one thing after another here,” said Miguel Conchas, president of the Laredo Chamber of Commerce. “It's the uncertainty that really plays havoc with businesspeople here in town and in Mexico.”

Copyright 2019 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.