The Unión Fronteriza de Operadores de Nuevo Laredo, also known as UFO A.C., gathered at 7 a.m. to protest long customs processing and crossing wait times.
Union president José Antonio García Fuentes said a group of about 20 members protested on the Mexican side of the bridge but left after about an hour because of pressure from Mexican police.
"We protested because we want to call the attention of the federal government in Washington and Mexico," García Fuentes said in Spanish. "This is our livelihood. The long lines don't let us make money."
García Fuentes said they get paid for each crossing, so he often tries to get to the World Trade Bridge hours before it opens. He said he's still had to wait five or up to eight hours to get through customs at the bridges.
"I'm not against them checking my truck, the cargo or me, but they should do it as quickly as possible," he said.
He said he thinks the long lines are due to unused lanes and inattentiveness from customs personnel.
"They're not the ones who have to sit in a truck for hours without air conditioning, in the heat or without a restroom," he said.
U.S. Customs and Border Protection said on Friday that beginning on Sunday, they would extend their hours of operation to be open from 8 a.m. to 4 p.m. They did not comment on the cause of the long waits.
García Fuentes said the union met with the Mexican bridge director on Saturday, but he won't be content until he sees a change.
"They listen, but they don't resolve anything," he said. "They can't give us an explanation for the long lines."
The union had said they were willing to block traffic through Sunday, when Mexican President Andres Manuel López Obrador was expected to tour government projects in Nuevo Laredo. But García Fuentes said they will instead seek to send a letter to López Obrador.
An estimated 14,000 commercial trucks cross the World Trade and the Colombia Solidarity bridges each day, according to the Laredo Economic Development Corporation.
The City of Laredo's bridge cameras showed trucks steadily moving through both sides of the World Trade Bridge on Saturday.