President Donald Trump threatened to deploy the military and close the southern U.S. border on Thursday as Hondurans and Salvadorans joined thousands of migrants in Guatemala hoping to travel north.

"I must, in the strongest of terms, ask Mexico to stop this onslaught — and if unable to do so I will call up the U.S. Military and CLOSE OUR SOUTHERN BORDER!" Trump wrote on Twitter.

Several thousand Honduran migrants moved this week through Guatemala, and some were trying to cross into Mexico on Thursday, according to local media. Some hope to eventually enter the United States to escape violence and poverty in Central America.