Trucks wait in queue for border customs control to cross into the U.S. at the Cordova-Americas border crossing bridge in Ciudad Juarez, Mexico April 8, 2019. REUTERS/Jose Luis Gonzalez

MEXICO CITY (Reuters) - Mexico’s foreign minister on Wednesday criticized hold-ups in the flow of goods and people at the U.S-Mexico border, and said he planned to discuss the matter with U.S. Department of Homeland Security officials later in the day.

After days of traffic delays at sections of the border that have alarmed businesses, Foreign Minister Marcelo Ebrard said the disruptions were raising costs for supply chains in both countries.

“Slowing down the flow of people and goods at the northern border is a very bad idea,” Ebrard said in a post on Twitter, using unusually frank language on an issue that has caused constant friction between Mexico and the administration of U.S. President Donald Trump.

Ebrard said his ministry would get in contact on Wednesday with the new leaders of the U.S. Department of Homeland Security. The department’s former secretary Kirstjen Nielsen, who had overseen Trump’s bitterly contested immigration policies during her tenure, stepped down at the weekend.

The border slowdowns have occurred after Trump late last month threatened to close the frontier if Mexico did not halt a surge in undocumented migrants reaching the United States.

On Monday, a judge in San Francisco said the Trump administration’s policy of sending some asylum seekers to Mexico while their claims worked through a backlogged immigration court system was not authorized by U.S. law.

The White House said on Tuesday it would appeal the ruling and that its policy was part of a “cooperative program extensively negotiated with the government of Mexico.”

However, in a sign of ongoing tensions over the issue, Mexico’s foreign ministry noted afterwards that the return of the migrants was a “unilateral” measure with which it did not agree but was allowing on a “temporary” basis.

On Wednesday morning, only one of six lanes for commercial vehicles was open at the Bridge of the Americas border crossing between Ciudad Juarez and El Paso, according to online data from the U.S. Customs and Border Protection.