The governor of Texas is facing growing calls to abandon a vehicle inspection program that has led to blockades and long queues at Mexico border crossings, threatening billions of dollars in trade at a time when supply chains are already under strain.

Mexican truck drivers have blockaded border crossings since Monday in protest against the additional security checks, which were announced by Governor Greg Abbott in a two-paragraph letter last week. Crossing times for commercial freight have slowed to 10, 20 or even 30 hours in some cases, Mexican industry bodies said.

The dispute has imperiled billions of dollars’ worth of goods moving between the countries. In total, more than US $440 billion in trade flows through Texas-Mexico border crossings each year, according to the Texas Center for Border Economic and Enterprise Development at the Texas A&M International University.

The commercial disruption comes amid a broader dispute over immigration between Abbott, a Republican, and the Democratic Biden administration.

Abbott said the additional inspections were aimed at stopping migrant smuggling and drug trafficking across the border, as well as increasing vehicle safety. He also framed the measures as a response to U.S. President Joe Biden’s decision to end pandemic-related migrant expulsions.

“This is going to dramatically slow traffic from Mexico into Texas. It is a byproduct of cartels crossing the border,” Abbott said in a news conference last week.

Texas’s Department of Public Safety said that within five days of Abbott’s order, it had inspected 3,443 commercial vehicles and put 807 of them out of service for safety violations.

Trade traffic at four critical ports of entry has been reduced to about one-third of the typical level, costing both countries income and competitiveness, Mexico’s foreign ministry said on Tuesday, adding that it rejected the inspection program.

U.S. Customs and Border Protection on Tuesday called Texas’ new measures “unnecessary” and said protests in Mexico had stopped all commercial traffic at the Pharr International Bridge. Northbound cargo traffic was also interrupted at Ysleta and New Mexico’s Santa Teresa crossing, it said.

The increased safety inspections piled further disruption on supply chains in industries from agriculture to automobiles that were already under stress because of the pandemic.

“The execution of this order has wreaked havoc up and down our supply chain,” the Texas International Produce Association said in a letter this week. “This is destroying our business and the reputation of Texas.”

Several Mexican industry groups said the checks had caused hours-long delays in crossing in some cases, with drivers often having to wait without food, water or bathrooms.

Mexico’s National Freight Transport Chamber on Tuesday called on Abbott to end the inspections to avoid a “collapse in international cross-border trade,” estimating that the delays at the Pharr bridge were costing $8 million a day.

Mexico’s National Agricultural Council said drivers would previously take about four hours to go through all the necessary border checks in Texas. Since the new measures came into effect, that has risen to as much as 30 hours.

The measures were designed to focus the federal government’s attention on immigration issues, said Raymond Robertson, director of the Mosbacher Institute for Trade, Economics and Public Policy at Texas A&M University. Even many conservatives in the state’s business community were pushing back against them, he added.

“There’s already been a lot of conservative people who are life-long Republicans who are really uncomfortable with what’s going on and I think they’re going to put pressure on the governor,” he said.

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