Trucks delivering goods from Mexico to the United States are facing up to eight hours of gridlock after a transfer of US border agents to immigration duties slowed the flow of commercial traffic at border crossings.
President Donald Trump took a step back on Tuesday (local time) from his threat to close the US southern border to fight illegal immigration amid pressure from companies worried a shutdown would inflict chaos on supply chains.
"We're going to see what happens over the next few days," Trump said.
He had threatened to close the border this week unless Mexico acted to curb a surge of asylum seekers from countries in Central America.
But the reshuffling of border agents, announced last week to process migrant families entering the US from Mexico, prompted delays of up to eight hours for trucks crossing from Mexico's Ciudad Juarez to El Paso, Texas.
"Industry is most affected by this situation, due to the millions in fines they have to pay when deliveries arrive late to clients," Manuel Sotelo, head of the truckers union in Ciudad Juarez, said.
Sotelo said the delays could even lead to the cancellation of contracts.
US Department of Homeland Security officials said the recent redeployment of 750 officers on the border to deal with a surge in migrants led to the slowing of legal crossings and commerce at ports of entry.
Mexico's foreign minister, Marcelo Ebrard, also noted commercial traffic at the US-Mexico border had slowed at several crossings.
Ebrard said the US government has told Mexico it is not going to shut down the border, but said his country would be prepared for that possibility.
Closing the border could disrupt millions of legal crossings and billions of dollars in trade. Auto companies have privately warned the White House in recent days it would lead to the idling of US auto plants within days because they rely on prompt deliveries of components made in Mexico.
Senate Republican leader Mitch McConnell warned Trump against such a move.
"Closing down the border would have potentially catastrophic economic impact on our country and I would hope we would not be doing that sort of thing," McConnell told reporters at Congress.