WASHINGTON (Reuters) – U.S. President Donald Trump on Tuesday threatened to withdraw funding and aid from Honduras if it does not stop a caravan of people that is heading to the United States.

“The United States has strongly informed the President of Honduras that if the large Caravan of people heading to the U.S. is not stopped and brought back to Honduras, no more money or aid will be given to Honduras, effective immediately!” Trump said on Twitter.

Up to 3,000 migrants crossed from Honduras into Guatemala on Monday on a trek northward, after a standoff with police in riot gear and warnings from Washington that migrants should not try to enter the United States illegally.

The crowd more than doubled in size from Saturday, when some 1,300 people set off from northern Honduras in what has been dubbed “March of the Migrant,” an organizer said. The migrants plan to seek refugee status in Mexico or pass through to the United States.

Reuters could not independently verify the number of participants, but images showed a group carrying backpacks and clogging roads near the border, some waving the Honduran flag.

The impoverished nations of Central America, from which thousands of migrants have fled in recent years, are under mounting pressure from Trump’s administration to do more to curb mass migration.

(Reporting by Doina Chiacu; Editing by Bernadette Baum and Susan Thomas)