The Mexican government said Thursday that the first migrants in a caravan that has drawn the ire of U.S. President Trump have reached their southern border with Guatemala. As many as 4,000 people are making their way from Honduras to Guatemala and north to Mexico, with their sights set on the U.S. border.

In a statement Thursday evening, the agency says officials are explaining the migrants' options and helping those who have requested refugee status to navigate the process.

Earlier Thursday, Mexican ambassador to the U.S. Geronimo Gutierrez called it a "humanitarian crisis."

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Mexican officials have said the Hondurans will not be allowed to enter as a group. They say individuals will either have to show a passport and visa - something few have - or apply for refugee status.

Mr. Trump has been pressuring Central American governments and more recently Mexico to stop the migrant caravan, and on Thursday he threatened to shut the U.S.-Mexico border if the migrants are not stopped.

At a rally in Montana on Thursday, Mr. Trump said he is "willing to send the military to protect our southern border if necessary." Mr. Trump also accused Democrats of thinking the migrants who come in will vote for Democrats.

"They're not so stupid when you think about it, right?" Mr. Trump said about Democrats.