(CNN) The Pentagon notified Congress Monday night that it has authorized the transfer of $1 billion to begin new wall construction along the US-Mexico border, drawing immediate objections from Democratic lawmakers.

A Pentagon budget reprogramming notification sent to Capitol Hill on Monday and obtained by CNN indicates that up to $1 billion will go toward building 57 miles of fencing, improving roads and other measures on the southern border.

The Department of Defense authorized the Army Corp of Engineers to begin planning and construction for the project Monday night. The department will direct the funds toward 18-foot-high fencing along the Yuma and El Paso sections of the border, according to a letter acting Secretary of Defense Patrick Shanahan sent to Secretary of Homeland Security Kirstjen Nielsen.

In February, President Donald Trump declared a national emergency in order to funnel billions of dollars to wall construction. As part of his announcement, he directed the use of counterdrug monies to partially fund new wall construction. Under the national emergency, other funds can also be dedicated to building the wall and related infrastructure, including military construction funds.

Monday's announcement was just the first $1 billion the administration is making available for wall funding. The administration said previously it plans to shift an additional $1.5 billion at some point in the future.

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