The month-long caravan that at one point gathered 1,500 immigrants from Honduras, Guatemala and El Salvador drew the wrath of President Donald Trump during its journey through Mexico.

Trump pressured Mexico to stop the migrants before they reached the border, linking Mexican efforts to stem the flow of Central Americans to the future of the North American Free Trade Agreement (NAFTA) currently being renegotiated in Washington.

The remaining 400 or so members of the caravan now face hard choices, whether to cross illegally into the United States, ask for asylum at the border or try to remain in Mexico.

"I feel a little cold. I feel anxious," said Jaime Alexander from El Salvador in the morning, shaking slightly on his way to the Tijuana, Mexico side of the border fence on a Pacific Ocean beach.