The US is to send an additional 2,000 troops to its border with Mexico, the Pentagon has announced. It will bring the total number of troops stationed on the southern border to about 4,300.
The Pentagon said the soldiers would help border-patrol agents, carry out surveillance work and install miles of razor wire.
It comes as President Donald Trump battles Congress for funds to build a wall along the border.
He says such a measure is needed to stop illegal immigration.
He struck a temporary deal last month to reopen government departments but has threatened to trigger another shutdown or declare a national emergency if his demands are not met. The current agreement expires on 15 February.
Mr Trump is expected to again highlight the issue in his annual State of the Union speech on Tuesday.
What is the latest?
The US defence department said 3,750 extra soldiers would be sent to the border, although many will replace troops already there. The first deployments took place in November.
“Additional units are being deployed for 90 days, and we will continue to evaluate the force composition required to meet the mission to protect and secure the southern border,” a Pentagon statement said.
Last Thursday, President Trump tweeted that extra forces were being sent to the border to stop migrants who he said were travelling in “caravans” and threatening an “invasion”.
What is happening at the border?
Officials in Texas recently revealed that nine migrants on hunger strike at an immigration detention centre were being force-fed.
Immigration officials are using plastic nasal tubes to feed some of the men, but relatives say it is causing severe nosebleeds and vomiting.
The detainees have refused food in protest against conditions at the El Paso Processing Center.
Immigration and Customs Enforcement (ICE) says a federal judge authorised the force-feeding last month.