(NewsNation) — Immigration advocates have described a scene of tension and confusion ahead of President Joe Biden’s scheduled first visit to the southern border in El Paso, Texas, Sunday afternoon.

El Paso has swiftly become the busiest of the Border Patrol’s nine sectors along the U.S. border with Mexico.

Large numbers of Venezuelans began showing up in September, drawn to the relative ease of crossing, robust shelter networks and bus service on both sides of the border, and a major airport to destinations across the United States.

U.S. authorities stopped migrants 53,247 times in November in the El Paso sector.

Around 300 migrants have taken refuge on the city’s sidewalks outside Sacred Heart Church, some of them afraid to seek more formal shelters, advocates say, amid new restrictions meant to crack down on illegal border crossings.

Biden signaled a tougher stance on migrants coming from Cuba, Haiti and Nicaragua, saying it would immediately start turning away people from those countries who cross the U.S.-Mexico border illegally, as it has done with Venezuelans.

Dylan Corbett, who runs the nonprofit Hope Border Institute, said the city is experiencing an increasing “climate of fear.”

Corbett said immigration enforcement agencies have already started ratcheting up deportations to Mexico, and he senses a rising level of tension and confusion.

The president’s new policy expands on an existing effort to stop Venezuelans from attempting to enter the U.S., which began in October.

Corbett said many Venezuelans have since been left in limbo, putting a strain on local resources. He said expanding those policies to other migrants will only worsen the circumstances for them on the ground.

“It’s a very difficult situation because they can’t go forward and they can’t go back,” he said. People who aren’t processed can’t leave El Paso because of U.S. law enforcement checkpoints; most have traveled thousands of miles from their homelands and refuse to give up and turn around.

“There will be people in need of protection who will be left behind,” Corbett said.

Following El Paso, Biden will be traveling on to Mexico City to meet with North American leaders on Monday and Tuesday.

The Associated Press contributed to this report.