The U.S. southern border has seen a sharp drop in migrant encounters entering between ports of entry at the southern border, according to a CBP source.

Newly sworn-in U.S. President Donald Trump said on Monday that he would declare illegal immigration a national emergency, send troops to the U.S.-Mexico border, and reinstate his "remain in Mexico" policy as part of a sweeping immigration crackdown.

The notion that America is being invaded has become the defining theme of Mr Trump’s immigration policy. Hours after his inauguration the president issued ten executive orders on immigration and border enforcement “to repel the disastrous invasion of our country”.