MATIAS ROMERO, Mexico (Reuters) - Central American migrants stranded on a journey through Mexico because of U.S. President Donald Trump’s pressure on the Mexican government say they will struggle on toward the United States, even as their “caravan” said it would disband in Mexico City.

Central American migrants, part of a caravan moving through Mexico toward the U.S. border, stand in line to register at a makeshift centre of Mexico's National Institute of Migration, in Matias Romero, Mexico April 4, 2018. REUTERS/Henry Romero

Fearful of the risks to children among the bedraggled and tired knot of travelers, the organizers of the annual caravan, U.S.-based advocacy group Pueblo Sin Fronteras, said it would end in the capital, not at the border as had been planned.

“It’s not because of Donald Trump,” said Irineo Mujica, director of Pueblo Sin Fronteras, which has staged the caravan since 2010 to draw attention to migrants’ rights and help them.

Mujica said the group did not want to put children on freight trains, which are traditionally used to cover part of the journey to the border. Nicknamed “la bestia” (the beast), the train is infamous for causing injury to migrants.

Trump has lashed out at the caravan, accusing Mexico of failing to stop illegal immigrants heading to the border.

The president took a hard line on illegal immigration during the 2016 election campaign and is frustrated by the failure of Congress to fund his long-promised border wall.

Trump would sign a proclamation on Wednesday ordering the deployment of the National Guard to the border with Mexico, Homeland Security Secretary Kirstjen Nielsen said.

Mexican officials, meanwhile, have screened people in the caravan, stalling it and dispersing migrants. The foreign ministry denied putting pressure on the migrants, saying that the caravan was breaking up of its own volition.

By mid-afternoon on Wednesday in the southern town of Matias Romero, migrants were sprawled in the fields singing songs or tying to sleep off the searing sun.

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Sitting in the dust was a seven-year-old boy who removed his dirty flip-flops and splayed his feet, revealing flaking and blackened cracks between his toes from days of walking with his mother and sister from El Salvador.

A number of the children in the caravan were suffering from diarrhea, vomiting, respiratory problems and dehydration, said a local doctor, Julio Cesar Iglesias.

Some migrants may get permits to stay, while others will be sent back to their home countries, the Mexican government says.

Hundreds of the migrants, many from Honduras, marched in Matias Romero on Tuesday evening to draw attention to their plight near the field where they have been bivouacked since the weekend.

There were shouts to oust Honduran President Juan Orlando Hernandez, whose disputed re-election victory in a November vote split the country.

International observers criticized the result due to serious concerns over vote-rigging, though Mexico and the Trump administration recognized it a few weeks later. Some migrants in the caravan saw no future for themselves in Honduras.

One of them, Maria Elena Colindres Ortega, an opponent of Hernandez and former member of the Honduran congress who is seeking U.S. political asylum, said the march on Tuesday aimed to show the migrants were not giving up.

“We’re marching and moving to prove to (Trump) that we are not afraid,” said Colindres Ortega, a mother of seven.

Migration officials on Wednesday continued to register names and issue permits to some migrants that give them 20 days to leave Mexico - a far shorter period than the caravan has taken to reach the U.S. border in previous years, organizers said.

The organizers said that on Sunday about 300 migrants, most of them men, left the group, and headed to the eastern state of Veracruz. There, according to three witnesses, four truckloads of immigration officials gave them 48 hours to disperse.