By Lisa Maria Garza

DALLAS (Reuters) - American citizens describing themselves as "deeply concerned" with Obama administration immigration policies plan a mass protest on Saturday to press their demand to seal the southern border by blocking traffic at more than a dozen U.S. crossings.

Demonstrators will attempt to stop incoming and outgoing traffic at 17 of the 63 locations in Texas, New Mexico, Arizona and California listed on the U.S. Customs and Border Protection website.

Rob Chupp, an organizer of the action publicized as "Shut Down All Ports Of Entry," said more than a thousand people are expected to gather across the several states at the same time, 8 a.m. PDT/10 a.m. CDT at targeted checkpoints, park their vehicles in every lane and turn them off.

Chupp said protesters planned to camp out indefinitely, while avoiding trespassing on federal property, and expect the most serious legal consequence to be a traffic ticket.

"If it's putting people's safety at risk then we would move, but other than that, we won't," Chupp said.

Chupp said a First Amendment area has no boundaries.

"We're not going to be at every port so people can still travel in and out of the country," he said.

Their demands include permanently sealing the southern border with an impenetrable razor wire or electric fence, giving border patrol agents authority to detain and remove immigrants who cross the border illegally and ending U.S. government assistance to undocumented immigrants.

Chupp denied media reports that armed militias would be present at the demonstration. Everyone is acting as an individual and is responsible for their own actions, including the legal possession of concealed firearms, he said.

"This is not an open carry rally," Chupp said.

Customs and Border Protection said in a statement it has been coordinating with local police departments to respond to any situation near the ports of entry such as temporary blockage of traffic at the international border crossings.

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"Our primary concern is to ensure the safety of our officers and the traveling public," the statement said.

Ruben Villarreal, mayor of Rio Grande City on the Texas border with Mexico, said he supports a right to peaceful protest but doesn't want demonstrators to obstruct roads or operations at the port of entry, where hundreds of millions of dollars of business is transacted every day.

"It's a lifeline to our country," Villarreal said. "It's a lifeline to our community."

(Reporting by Lisa Maria Garza; Editing by David Bailey and Sandra Maler)