The ever-growing caravan of Central American migrants swelled on Sunday to an estimated 7,000 people, who are largely dedicated to traveling north in the hopes of reaching the United States.

On Sunday they trekked through Mexico, chanting, "Si se pudo," Spanish for, "Yes, we could!"

President Donald Trump has raged against the governments of Honduras, Guatemala, and El Salvador, whom he accused of not doing enough to stop the mass exodus of Central Americans.

Trump has threatened to cut aid to those countries if the caravan makes it to the US border, though he praised the Mexican government for deploying federal police officers to manage the situation.

"Full efforts are being made to stop the onslaught of illegal aliens from crossing our Southern Border. People have to apply for asylum in Mexico first, and if they fail to do that, the U.S. will turn them away. The courts are asking the U.S. to do things that are not doable!" he tweeted Sunday. "The Caravans are a disgrace to the Democratic Party. Change the immigration laws NOW!"

If they stop us now, well just come back a second time

Though Mexico has tried to prevent the migrants from crossing illegally, and ordered them to request asylum from immigration officials at the border crossings, only several hundred did, according to NPR. Roughly 1,500 of the caravan members remained on the Guatemalan side of the Mexican border.

Thousands of others entered Mexico illegally, crossing the Suchiate River, between Guatemala and Mexico, by swimming or taking rafts. A number of the migrants voted by a show of hands on Saturday, once they reached Mexico, to continue heading north, The New York Times reported.

"We want to get to the United States," one 17-year-old Honduran, Maria Irias Rodriguez, told The Times. She said she was traveling with her two young children and husband. "If they stop us now, we'll just come back a second time."

The growing caravan and seeming inability to stop it highlights a number of complex issues at play: The labyrinthine US asylum system, which the Trump administration loathes for its protections against detaining and quickly deporting children; the gargantuan task of securing a 2,000-mile border with Mexico; and the often desperate circumstances in the countries that prompt people to flee, which US government officials recently visited Guatemala to address.

Meanwhile, Mexico's president-elect, Andres Manuel Lopez Obrador, said Sunday that the US, Canada, and Mexico should strike a deal to invest in Central American development, according to the Associated Press.

"He who leaves his town does not leave for pleasure but out of necessity," he said.

Lopez Obrador, who takes office December 1, ran on a pro-immigration platform, promising jobs and work visas in Mexico to Central American migrants.