WASHINGTON – President Donald Trump’s decision to declare a national emergency so he can draw on Pentagon funds for the border wall presents a challenge for the Defense Department, which faces difficult choices about what projects and activities to scrap or delay to free up the more than $6 billion Trump wants to take from the military budget.

Trump intends to draw $3.6 billion from military construction funds and $2.5 billion from a military drug interdiction program to help build 234 miles of new barriers along the border. That military money would be used in addition to the $1.375 billion that Congress included for fencing in a recent bill and some $600 million he wants to pull from a Treasury drug forfeiture fund, for a total of more than $8 billion. A recent study found that the border wall would cost at least $15 billion and as much as $25 billion in total.

The efforts to tap the Pentagon’s budget under emergency powers essentially amount to an end-run around Congress, which traditionally holds the power of the purse in Washington and so far has refused to appropriate the amount of money Trump wants for the wall.

Officials at the Pentagon for weeks have been going through the books to figure out which projects should be discarded or frozen to pay for the wall, should the president tap military funds. In a statement, Navy Capt. Bill Speaks said the department was reviewing options to enable border barrier construction. He said it “would be inappropriate to comment further on those efforts at this time.”

In a news conference at the White House on Friday, Trump brushed off the possibility that the funds he plans to take from the Pentagon budget would prevent members of the armed forces from receiving the technology or housing they need. Trump said certain funds were being used at the discretion of generals, and some of the generals think this is more important.

“I was speaking to a couple of them,” Trump said. “They think this is far more important than what they were going to use it for. I said, ‘What were you going to use it for?’ And I won’t go into details, but it didn’t sound too important to me.”

Trump said he secured a $700 billion budget for the Pentagon in his first year in office and a $716 billion budget during his second year, and pledged to continue building up the military with a “pretty big” budget this year, too. He characterized the wall funding he was taking as a small amount.

“When you think about the kind of numbers you’re talking about, so you have $700 billion, $716 billion, when I need $2 billion, $3 billion out of that for a wall . . . when you have that kind of money going into the military, this is a very, very small amount that we’re asking for.”

The move to draw on Pentagon funds without congressional approval, which almost certainly will end up challenged in court, has provoked ire among Democrats and Republicans alike on Capitol Hill, who generally authorize annual funding of the U.S. military with bipartisan support.

Rep. Adam Smith, D-Wash., chairman of the House Armed Services Committee, accused the president of stealing money from projects that support the military and their families without congressional approval, all for a political stunt driven by misguided priorities.

“It is clear that there is no national emergency – only a manufactured crisis – and there has been no attempt to explain how the wall has anything to do with supporting U.S. military needs, as the law intends,” Smith said in a statement. “From the beginning, President Trump’s obsession over a border wall has been based on misguided anti-immigrant fervor, not U.S. national security.”

Rep. Mac Thornberry, R-Tex., the highest-ranking Republican on the committee, said in a statement that the decision to send military personnel and resources to the southern border by the past five administrations made it clear that Congress was not adequately funding the agencies that control who and what crosses the border. But he urged the president not to draw on military funds.

“Doing so would have detrimental consequences for our troops as military infrastructure was one of the accounts most deprived during the Obama-era defense cuts,” he said. “And it would undercut one of the most significant accomplishments of the last two years – beginning to repair and rebuild our military.”

The move by Trump to draw funds from the Pentagon’s construction budget comes amid an outcry over the decrepit living conditions that many military families face on bases. A recent survey found instances of black mold, lead and vermin infestations in privatized military housing, which lawmakers described as shocking and infuriating.

Sen. Tim Kaine, D-Va., a member of the Senate Armed Services Committee, sent a letter to acting defense secretary Patrick Shanahan noting that the Pentagon recently said the military had a maintenance backlog of over $116 billion, with 23 percent of the department’s facilities in poor condition and another 9 percent in failing condition.

Kaine expressed concern that Trump was seeking to take about a third of the roughly $10.5 billion Congress devoted to military construction this year, even as the Pentagon must spend money to fix the housing problems and rebuild facilities affected by hurricanes in Florida and North Carolina.

“I am concerned that a project that the president stated would be paid for by Mexico will now be borne by military servicemembers and their families, as they will be forced to remain in ‘poor’ or ‘failing’ conditions,” Kaine wrote. “The safety and well-being of our forces and their families is the supreme responsibility of every commander in the military; it should be no different for the commander-in-chief.”

Trump administration officials, in a call with reporters on Friday, said the Pentagon wouldn’t be drawing on projects that impact the readiness of the force.

“We would be looking at lower priority military construction projects. We would be looking at ones that are to fix or repair a particular facility that might be able to wait a couple of months into next year,” a senior Trump administration official said. “So we’re going through a filter to ensure that nothing impacts lethality and readiness on the part of our military construction budget.”

Trump is targeting $3.6 billion from the military construction fund because an obscure statute in U.S. code authorizes the defense secretary to undertake military construction projects “not otherwise authorized by law” in support of any troops deployed in a national emergency.

The law limits the administration to so-called unobligated funds – or money that Congress has appropriated for military construction projects but which has yet to be committed by contract.

Trump would tap the $2.5 billion from the drug interdiction fund through a separate set of authorities that don’t require a national emergency declaration. They allow the Pentagon to support federal, state and foreign agencies to prevent drug trafficking.

The amount Trump is seeking from the drug interdiction program currently exceeds what is in that account for this fiscal year by about $1.5 billion, meaning the Defense Department would need to redirect the difference from other parts of its budget. That would happen through the reprogramming process, by which the Pentagon can redirect existing funds to new projects.

Though Congress allows the Pentagon to reprogram funds over the course of a fiscal year to give the military flexibility and account for changing threats and needs, the Defense Department can reprogram a maximum of $4 billion in the fiscal year. By reprogramming $1.5 billion for the wall, the Pentagon would expend a lot of its reprogramming allotment, potentially reducing budget flexibility in other areas.