(CNN) – The migrant caravan heading north toward the U.S. may be facing a new hurdle.
It may take weeks to materialize, but a standoff at the border could be brewing – because hundreds of troops are expected to be sent to stop the migrants.
"We have to protect our borders. We don't have borders, we don't have a country," President Donald Trump said at a rally.
Many men, women and children are marching through southern Mexico toward the U.S. Some are about 1,000 miles away.
Trump tweeted that they should return home and “apply for citizenship like millions of others are doing!”
U.S. Rep. Matt Gaetz, R-FL, echoed Trump’s sentiments.
"The sad thing is, like, OK, if 99 percent of them are wonderful people who are desperate, and 1 percent of them are going to go commit some heinous act of violence, that's still reason to stop the caravan," Gaetz said.
Homeland Security Secretary Kirstjen Nielsen, appearing on Fox News, said her department has asked for hundreds of troops to help prevent the migrants from entering the U.S.
"What we've asked them to do is help to bolster our capabilities,” she said. “So, we've asked for some air support, for some logistics, some planning, vehicle barriers, engineering, ways in which we can make sure that I can protect my officers and agents."
Sources said the troops will be there to support civil authorities, but they can defend themselves if needed.
Border Patrol officers, however, will lead the effort to stop illegal immigration.