Acting Pentagon chief Patrick Shanahan said on Tuesday he had authorised $1 billion to build part of the wall sought by US President Donald Trump along the US-Mexico border.

The Department of Homeland Security asked the Pentagon to build 57 miles (92 kilometers) of 18-foot (5.5-meter) fencing, build and improve roads, and install lighting to support Trump’s emergency declaration as concerns the border.

Shanahan “authorized the commander of the US Army Corps of Engineers to begin planning and executing up to $1 billion in support to the Department of Homeland Security and Customs and Border Patrol,” a Pentagon statement read.

Earlier in February, Trump had declared a State of Emergency to fund his campaign promise of building Mexico border wall, after the Congress resolutely refused to give him the money he wanted.

Trump backed away from his threat to again shut down the government if the legislature did not vote $5.7 billion for the border wall and approved the bipartisan funding bill without the allocation, and instead resorted to the Emergency.

The National Emergencies Act allows the President to declare a national emergency and unlock a stash of funds by invoking certain statutory authority.

The US House and Senate legislators had earlier reached an agreement “in principle” to provide $1.375 billion for barriers at the Mexico border, a figure far lower than the $5.7 billion that President Donald Trump had demanded, to avert another government shutdown.

The White House and congressional leaders have struggled for months to reach an agreement on a government funding bill because of major differences between Democrats and Republicans over immigration policy.

Trump called for using $5.7 billion in taxpayer money to construct more than 200 miles of a wall along the US-Mexico border.

Democrats objected to this and Trump forced the first partial government shutdown on December 22, 2018, to try to exert pressure on Congress to act.

(With agency inputs)