MATIAS ROMERO, Mexico (REUTERS) - Impoverished Central American migrants travelling in a "caravan" through Mexico that angered US President Donald Trump said they would stick together for safety even though the group will end its journey in Mexico City rather than at the US border.

Since peaking at around 1,500 people, the caravan has dwindled under pressure from Trump and Mexican migration authorities, which vowed to separate those migrants with a right to stay in Mexico from those who did not.

By issuing permits to the migrants, authorities shielded them from imminent deportation from Mexico.

By Thursday morning (April 5), migrants were boarding buses to leave the town of Matias Romero in the southern state of Oaxaca, where their journey was held up by authorities at the weekend.

Salvadoran Andres Rodriguez, 51, waited with a small backpack and a gallon of water in a field sprawling with men, women and children, mulling over a document that gave him 20 days to reach any border out of the country.

Despite knowing the permit protected him, and that travelling alone would be faster, he feared if he left the caravan he would be exposed to the robbery and assault that befall many migrants on the long slog to the US border.

"It's much safer," he said. "Everyone is supporting us. One person alone is much more vulnerable. Much more dangerous."

Rodriguez, a builder, said he fled his home in El Salvador in the middle of the night with only the clothes on his back, a few dollars, a nephew, and his son, a student who had received a written death threat from a gang he had refused to join or pay.

"To be young, in my country, is a crime," Rodriguez said. "I'm old - they'll do nothing to me. But to my son, if we go back ... they'll kill him."

Plagued by gang violence and poverty, El Salvador and neighbouring Honduras have murder rates that are among the world's highest.

Trump's tweets criticising the caravan have showered it in far more publicity than its organisers, US-based advocacy group Pueblo Sin Fronteras, ever expected. But his proposal to militarise the border has sparked a diplomatic row with Mexico.

Mexico's President Enrique Pena Nieto rebuked Trump on Thursday over his plan to send National Guard troops to the border, urging Trump not to vent his domestic political"frustration" on Mexico.
Stranded in Matias Romero since Sunday, a handful of women and children boarded a bus before dawn on Thursday, headed for the central city of Puebla, where the caravan was due to make another stop before concluding its journey in Mexico City.

By mid-morning, others packed bags in a field strewn with discarded clothes and trash as two more buses waited, but only for those who could afford a ticket.
The caravan, which set off from Mexico's southern border on March 25, aims to raise awareness about the plight of migrants, and has been running annually since 2010, the government said.

Once in Puebla, organisers plan to hold a three-day conference with US and Mexican immigration attorneys.

On a street just outside the park, 30-year-old Guatemalan Manuel Flores brandished a temporary Mexican visa, but said he would stay with the caravan regardless. "I don't even need to be here, but I'm staying for them - for my family. Because they need this. They can't go home," he said, pointing to a group of seven new friends from Honduras and El Salvador, with whom he had cooked a great vat of seafood soup.

Bonded by the travails of their odyssey, they were already discussing setting up a restaurant together in Texas.