Hundreds of Central American migrants are gathering in Tijuana, Mexico and plan to cross the border into the U.S., despite strong warnings from President Donald Trump to keep them out.
The migrants are part of a caravan that crossed into Mexico and have reunited at the border town, according to Reuters.
The first groups of migrants plan to try to enter the U.S. on Sunday, The Associated Press reported.
And it could spark a possible showdown with the Trump administration.
"I have instructed the secretary of Homeland Security not to let these large caravans of people into our country," Trump said this week in a tweet. "It's a disgrace."
And the AP reported Trump and senior aides have portrayed the caravans as a serious threat.
Reuters noted the timing could end up complicating talks to renegotiate the North American Free Trade Agreement (NAFTA).
The wire service said Trump has threatened to scrap the agreement if Mexico does not crack down on Central Americans coming through.
Meanwhile, U.S. Secretary of Homeland Security Kirstjen Nielsen said she would prosecute anyone who made a "false immigration claim" or illegally entered the U.S.
The AP said U.S. Customs and Border Protection has room to hold about 300 people at the crossing.
Busloads of migrants began arriving in Tijuana on Tuesday. Associated Press estimated the number has swelled to nearly 400.
One of those hoping to get into the U.S. is Jovanne Torres from El Salvador. But he admitted Trump's attacks on the caravan makes him worried about whether he'll succeed.
"Trump's words have made it difficult for us," he said.
Gabriela Hernandez left Honduras to try to live in Houston with a relative. But she is also concerned about Trump's words, CBS News reported.
"I see it as something really sad, because I don't understand how a child this age can make things difficult for him," said Hernandez, who is two months pregnant.