The US Defense Department on Tuesday said it would authorize construction of roughly 20 additional miles (about 32 kilometers) of Mexico border fence, roads, and lighting in Arizona and California, Politico reported.

The Pentagon said in a court filing that due to “lower-than-expected contract costs,” it would be able to construct the additional barriers with money left over from a pot of $2.5 billion that was redirected to the border from a counter-drug fund.

Building a barrier and a wall along the Mexican border was one of the main election promises of incumbent US President Donald Trump.