The US government is prepared to handle a potential gush of migrants from next month when Covid-19 rules will no longer be used to push nearly all undocumented border-crossers back into Mexico, officials said Tuesday.

President Joe Biden's administration will implement a "comprehensive strategy" to deal with a surge in asylum seekers and refugees seeking to enter the country after the May 23 end to Title 42, the public health order used to bar immigrants wholesale since the early days of the coronavirus pandemic, the officials said.

Instead, migrants will be allowed to apply for humanitarian entry under Title 8 authority, a shift which immigration critics say will see border authorities overwhelmed and perhaps hundreds of thousands of migrants allowed to stay while their applications are considered.

Meanwhile, the officials said, those without legitimate claims -- and especially migrants who repeatedly cross the border illegally -- will be subject to legal charges.

"When Title 42 is lifted, normal operations at the border under Title 8 processing will be restored," a senior administration official told reporters on grounds of anonymity.

Following the change, "asylum and other legal migration pathways will remain available to those seeking protection, and those who don't qualify will be promptly removed," the official said.

In a conference call with reporters, officials acknowledged that Title 42, first implemented by the previous administration of Donald Trump and criticized by immigration advocates, could remain in place after a Louisiana court said it would issue a temporary restraining order in a lawsuit by opposition Republicans.

The Biden administration would abide by that order when it comes, another senior official said.

A child sleeps in a tent in a camp for migrants near the US border in Tijuana, Mexico.
A child sleeps in a tent in a camp for migrants near the US border in Tijuana, Mexico. AFP / Patrick T. FALLON

But "it really makes no sense to us," the official said, because keeping Title 42 would prevent the government from using powers of expedited removal under Title 8.

That "is going to prevent us from adequately preparing for the aggressive application of immigration law when the public health order expires," the official said.

Immigration pressure has surged over the past two years, with border officials pushing back each month as 220,000 people seeking to cross the border from Mexico.

Most of them are from Central and South America, but many come from as far as South Asia and, most recently, Ukraine.

The officials said they were boosting coordination with Central American countries where most of the migrants transit to slow the northward flow and return migrants to their home countries, and broadening efforts to crack down on migrant smuggling groups.

They are also boosting capacity to process refugee requests to stay.

But they acknowledged that large migrant camps just into Mexico could unleash a surge of border crossing if and when Title 42 is removed.

"We are definitely aware of the individuals who are currently in Mexico and are actively planning in order to respond, post-Title 42," the second official said.