Marines patrol during work to fortify the border structure that separates Tijuana, Mexico, behind, and San Diego, near the San Ysidro Port of Entry, Nov. 9, 2018, in San Diego.
Marines patrol during work to fortify the border structure that separates Tijuana, Mexico, behind, and San Diego, near the San Ysidro Port of Entry, Nov. 9, 2018, in San Diego.

The Pentagon is expecting a request from the White House to do more to help prevent illegal migration across the U.S. border with Mexico, the acting defense secretary said Wednesday. 
 
Some 6,000 troops are now posted along the border, and the armed forces have been tasked with arranging military accommodation for 5,000 unaccompanied minors. 
 
Trump, who made stemming arrivals of undocumented migrants a plank of his 2016 election campaign, declared a national emergency on the border in February as a way to sidestep Congress for money to build a wall along the frontier. 
 
"I'm going to work very closely with the acting [homeland security] secretary," acting Defense Secretary Patrick Shanahan said Wednesday. He was referring to Kevin McAleenan, the replacement for Kirstjen Nielsen, who resigned over the weekend as department secretary. 
 
"What I would say is, as the situation there deteriorates, it's pretty elastic in terms of demand on us, so I would expect shortly here to have another request for assistance," he told reporters. 
 
Shanahan has already released almost $1 billion to build a section of Trump's wall, cash diverted from the Pentagon budget for combating the drug trade. 
 
The Pentagon announced Tuesday that it had awarded two contracts worth $976 million for work on the proposed new wall and repairs to existing barriers in New Mexico and Arizona. 
 
Shanahan said he did not rule out more military funds being assigned soon to wall construction.