Federal government employees, contract workers and other demonstrators march during a "Rally to End the Shutdown" in Washington, January 10, 2019.

President Donald Trump has been briefed on a plan that would use the Army Corps of Engineers and a portion of $13.9 billion of Army Corps funding to build 315 miles of barrier along the U.S.-Mexico border, according to three U.S. officials familiar with the briefing.

The money was set aside to fund projects all over the country including storm-damaged areas of Puerto Rico through fiscal year 2020, but the checks have not been written yet and, under an emergency declaration, the president could take the money from these civil works projects and use it to build the border wall, said officials familiar with the briefing and two congressional sources.

The plan could be implemented if Trump declares a national emergency in order to build the wall and would use more money and build more miles than the administration has requested from Congress. The president had requested $5.7 billion for a wall stretching 234 miles.

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Under the proposal, the officials said, Trump could dip into the $2.4 billion allocated to projects in California, including flood prevention and protection projects along the Yuba River Basin and the Folsom Dam, as well as the $2.5 billion set aside for reconstruction projects in Puerto Rico, which is still recovering from Hurricane Maria.

Senior Defense Department officials discussed the proposal with Trump during his Thursday flight to the southern border, according to officials familiar with the briefing.

Trump was informed that the Army Corps could build 315 miles of border wall in about 18 months, according to officials familiar with the planning. The barrier would be a 30-foot bollard-style wall with a feature designed to prevent climbing, the officials said.

The Corps would focus first on the heavily trafficked border areas along the Rio Grande Valley in Texas, in San Diego and El Centro in California, as well as Yuma, Arizona.

The White House did not immediately return a request for comment.

A source on Capitol Hill said if the president moves to pull money from Corps of Engineers civil works projects, Democrats in Congress are likely to submit legislation to block the money from being reallocated.

Asked about the proposal, a Democratic staffer warned that taking money from civil works projects in the U.S. will put American lives at risk.

"Hundreds of thousands of people will be at risk if there is a strong or wet winter in these flood areas and the protection projects haven't been completed," the staffer said.

Rep. Nydia Velázquez, D-N.Y., said the Democrats would fight "with every ounce of energy we have" to stop the president from using Army Corps funds to build a southern border wall.

"It would be beyond appalling for the president to take money from places like Puerto Rico that have suffered enormous catastrophes, costing thousands of American citizens lives, in order to pay for Donald Trump's foolish, offensive and hateful wall," Velázquez said. "Siphoning funding from real disasters to pay for a crisis manufactured by the president is wholly unacceptable and the American people won't fall for it."