The White House says it will ask Congress for $18 billion over the next decade to build more than 300 miles of a new border wall along the U.S.-Mexican border.  The figures are the first hard numbers suggested by the White House and came in response to congressional negotiators, who are trying reach an agreement with Democrats to fund the government after January 19.

Associated Press:

Trump has promised "a big, beautiful wall" with Mexico as a centerpiece of his presidency but offered few details of where it would be built, when[,] and at what cost.  His administration asked for $1.6 billion this year to build or replace 74 miles (118 kilometers) of fencing in Texas and California, and officials have said they also will seek $1.6 billion next year.

The 10-year plan, first reported by The Wall Street Journal, resulted from discussions with senators who asked the agency what it would take to secure the border, the official said.

It comes as the administration intensifies negotiations in Congress on a package that may include granting legal status to about 800,000 people who were temporarily shielded from deportation under an Obama-era program, Deferred Action for Childhood Arrivals.

Trump said last year that he was ending DACA but gave Congress until March to deliver a legislative fix.

The plan on border security came in response to a request by U.S. [s]en. Jeff Flake, said Jason Samuels, a spokesman for the Arizona Republican.

An administration official confirmed [that] the document was prepared at the request of congressional negotiators and said funding for the wall and other security measures must be part of any legislative package on immigration.  The official spoke on condition of anonymity because the plan has not been made public.

Homeland [s]ecurity [s]ecretary Kirstjen Nielsen told The Associated Press on Tuesday that the wall would be "first and foremost" in any package that includes new protections for DACA recipients.  She also said the administration wanted to close "loopholes" on issues that include handling asylum claims and local police working with immigration authorities.

Nielsen called the $3.2[-]billion requests for fencing during the administration's first two years a down payment.

"This is not going to get us the whole wall we need, but it's a start," she said.

The proposal to build just 300 miles of a wall along a 2,000-mile border doesn't seem like much.  But it is probable that the entire span of the border does not need a new wall.  About half the border is already covered by some kind of barrier.  Some of that may be replaced with a wall, but how much can be used if we enhance our technological means to guard the border?

This is why the White House has to get down to brass tacks on how much a wall is going to cost – how many miles, what kind of wall, etc.  The new funding will be a down payment on what is expected to be more than 850 miles of new wall construction, with security upgrades elsewhere along the border.

The negotiations between the two parties to fund the government past January 19 have now come down to horse trading.  Democrats may accept funding for the wall if Republicans agree to legalize DREAMers.  That may work this time.  But what happens the next time Trump has to go to Congress to get funding for the wall?  Democrats will look to hold wall funding hostage for some other issue.

But getting started on building the wall is what Trump is focusing on now, and the battle lines are clearly drawn.