Tens of thousands of US law enforcement personnel have been deployed to the border with Mexico, officials said Wednesday, as waiting migrants voiced confusion and anger over a looming change to entry rules.

The United States is girding for a surge in people claiming refuge from political persecution, climate-related disaster and poverty when pandemic-era restrictions expire overnight Thursday into Friday.

In the Mexican border town of Ciudad Juarez, Venezuelan construction worker Michel said he felt trapped and frustrated after many failed attempts to use the new phone app meant to process asylum requests once the rules lapse.

"We don't know what's happening," he told AFP after a dangerous overland journey from South America with his wife and five-year-old daughter. "They're making things more difficult."<

<< Read more: Title 42: What is it and how did the US use it to curb migration >>

About 24,000 border police and 1,100 processing personnel have been activated -- double the number a year ago, and the Pentagon has sent 1,500 extra troops to reinforce 2,500 already in place.

Alejandro Mayorkas, Secretary of Homeland Security, said the US government was "clear eyed" about the challenges of ending the Covid restrictions known as Title 42.

"Even after nearly two years of preparation, we expect to see large numbers of encounters at our southern border in the days and weeks after May 11," he told reporters Wednesday.

"We are already seeing high numbers of encounters in certain sectors."

'I couldn't wait any longer'

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