President Donald Trump said Sunday that "full efforts" were under way to halt the progress of thousands of Honduran migrants toward the United States.
"Full efforts are being made to stop the onslaught of illegal aliens from crossing our Souther(n) Border," Trump tweeted.
"People have to apply for asylum in Mexico first, and if they fail to do that, the US will turn them away. The courts are asking the US to do things that are not doable!
"The Caravans are a disgrace to the Democrat Party. Change the immigration laws NOW!"
Trump has warned that he would cut aid to the region, deploy the military and close the US-Mexican border if authorities do not stop them.
Mexico has vowed to detain any migrants who cross without visas, though it has also said it will process their asylum requests, and has asked for the UN refugee agency's help in doing so.
Trump has made curbing illegal immigration a keystone of his presidency.
Barely a week goes by without him warning about the danger posed by ultra-violent Central American gangs like MS-13, while chants of "build the wall" are a staple of his pre-midterm elections campaign rallies.