The Pentagon has sent hundreds of troops to the border with Mexico to prevent the entry of a convoy of immigrants, AFP reported.
US President Donald Trump said Thursday he was "moving the army" to protect the US border as a convoy of Central American immigrants continued to travel through Mexico en route to the United States.
"The army has moved for this national emergency ... they will be stopped," Trump said on Twitter.
Thousands of men, women and children seeking to escape violence, poverty and corruption in their countries continued their arduous journey towards the far-off American border.
People marched under the moonlight on Thursday night from the Mapestepic region near the Guatemalan border in southern Mexico.
An official in the town said 5,300 immigrants were in Mapestepec on Wednesday evening, while another group of 1,000 people started a similar flight from Guatemala.
On Monday, Trump said he had notified the "border guards and the army" that the immigrant convoy was a national emergency.
A federal law dating back to the 1870s forbids the military and other major branches of the armed forces from carrying out civil law on US territory except with congressional authorization.
But the armed forces can provide support services to law enforcement agencies, and have already done so from time to time since the 1980s.