SAN FRANCISCO MENENDEZ, El Salvador (Reuters) - About 2,000 migrants set off on foot from El Salvador’s capital on Wednesday, the latest of several groups of Central Americans heading to the United States, even as U.S. President Donald Trump increased pressure to halt their flow.

Men and women from the two groups of Salvadorans that departed San Salvador pushed baby strollers or bore children on their shoulders. On Sunday, a separate group of about 300 people set off from the city.

Some, such as 42-year-old Luis Geovanni Vindel, a salesman from the central city of Zacatecoluca, moved on quickly, hitching rides alone toward the Guatemalan border.

“We’re already one step away from Guatemala, and soon into Mexico,” said Vindel, limping forward with a cane on a prosthetic leg in the municipality of San Francisco Menendez.

A larger U.S.-bound caravan, which left northern Honduras in mid-October is moving north at about 30 miles (48 km) a day through southern Mexico. It has become a major campaign issue ahead of U.S. congressional elections on Nov. 6.

Mexico’s Interior Minister Alfonso Navarrete on Wednesday put the size of the first caravan at 2,800 to 3,000, below the government’s previous estimate of about 3,500. Participants in the caravan have put the number significantly higher.

Dozens of the men, women and children in that caravan told Reuters they were abandoning their homelands to seek asylum from a mixture of poverty, violence and corruption.

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“We’re now in an unprecedented situation in the country,” Navarrete told reporters in Mexico City. “This is not merely a caravan ... it’s a migratory exodus.”

The bulk of illegal immigrants intercepted at the U.S. border are from El Salvador, Guatemala and Honduras. Trump said he could send up to 15,000 troops to the U.S.-Mexico border, which is already heavily policed by border guards.

“It scares us a little. But since we’re seeing a ton of people going together, we can help one another to cross,” said Jose Machado, a migrant departing from San Salvador, his backpack stuffed with clothing and toiletries.

Trump, who has threatened to slash U.S. aid to Central America and close the U.S. border with Mexico, said in a tweet on Wednesday that Mexico needs to keep up efforts to discourage the migrants, who he described as “tough fighters.”

A clash at the Mexico-Guatemala border on Sunday left one migrant dead and several law enforcement officers injured.

“Mexican soldiers hurt, were unable, or unwilling to stop Caravan. Should stop them before they reach our Border, but won’t!” Trump said on Twitter.

White House press secretary Sarah Sanders on Wednesday praised Mexico’s actions to slow the movement of people, but told Fox News: “They can do more.”

Police estimated the two groups leaving San Salvador numbered around 1,000 each. One left around dawn, followed by the second later in the morning.

Some waved Salvadoran flags as motorists honked in support and shouted “God bless you.”