AMNA NAWAZ: Welcome to the "NewsHour."

A deadline is at hand tonight for migrants hoping to enter the U.S. from Mexico.

The hours are counting down to the end of COVID-19 curbs on asylum seekers.

GEOFF BENNETT: In its place, the Biden administration is promising a crackdown on illegal crossings.

That, in turn, made this a day of desperation for many.

Lisa Desjardins has our report.

LISA DESJARDINS: Massive lines and increasing tension at the southern U.S. border today, as both migrants and Border Patrol prepare for a major policy shift.

The pandemic era restrictions known as Title 42 have been used to deny asylum seekers for the past three years on the grounds of protecting public health.

Those restrictions expire at midnight tonight.

Amid confusion, some migrants fear what that could mean.

NESTOR VILLALOBOS, Venezuelan Migrant (through translator): We don't know how it's going to be.

Maybe it's easier to enter here or maybe it's more complicated.

In truth, we have uncertainty.

We are here, and we do not know what will happen.

Hopefully it will be easier for the migrant, because, at the moment, it is very difficult.

LISA DESJARDINS: For months, concern has mounted, as migrants have rushed to the border in record droves.

Across from Brownsville, Texas, crowds hoisted belongings overhead as they traversed the Rio Grande and stood face to face with U.S. troops separated by razor wire.

Yesterday, overwhelmed holding facilities near the border began releasing detainees, telling them to return for processing within 60 days.

The Biden administration says its replacement policy, known as Title 8, will both crack down on illegal crossings and foster legal pathways for migrants.

Secretary of Homeland Security Alejandro Mayorkas spoke at the White House.

ALEJANDRO MAYORKAS, U.S. Secretary of Homeland Security: We prepared for this moment for almost two years, and our plan will deliver results.

It will take time for those results to be fully realized, and it is essential that we all take this into account.

LISA DESJARDINS: No coincidence, on Capitol Hill... REP. KEVIN MCCARTHY (R-CA): On this about, vote, the yeas are 219, the nays are 213.

LISA DESJARDINS: ... House Republicans narrowly passed a sweeping Secure the Border bill.

Numbered H.R.2, it would resume building a border wall, add more Border Patrol agents, allow for indefinite family detention, and insist most asylum seekers remain in their home country or be detained while their claims are reviewed.

Debate was substantive and sharp.

REP. DEBBIE WASSERMAN SCHULTZ (D-FL): I urge my colleagues to reject this legislation.

It would brutally harm children for the sake of cheap political points.

Our border should be governed by laws upholding argumentative, not by demagogues promoting bigotry.

REP. JUAN CISCOMANI (R-AZ): H.R.2 gives our agents and officers the resources they desperately need, closes loopholes in an abused asylum system and protects innocent children from harm.

This bill is a step away from the chaos we are seeing and a step closer to helping others achieve the American dream I have been so blessed to live.

LISA DESJARDINS: The bill is not expected to get a vote in the Senate.

But the issue is expected to remain heated in Washington and across the country.

For the "PBS NewsHour," I am Lisa Desjardins.