The top tube of a border wall prototype falls during demolition at the border between Tijuana, Mexico, and San Diego on Feb. 27, 2019. (Gregory Bull/AP)

A senior defense official told lawmakers Wednesday that the Pentagon will not cancel any approved military construction projects to get money for President Trump’s border wall. The Pentagon may delay some projects, but will seek new money for them in the president’s upcoming budget request, said Robert McMahon, assistant secretary of defense for sustainment.

“No currently authorized military construction projects will be canceled,” McMahon said at a House Appropriations subcommittee hearing. “While some may be deferred, the budget request will include a request for funds to replenish these accounts.”

McMahon’s comments amounted to the first public promise from a top Pentagon official that there will be no outright cancellation of pending military construction projects in service of Trump’s wall. The national emergency declaration Trump issued this month allows him to tap money from a Pentagon account that funds projects ranging from hangar construction to base rehabilitation at military installations around the country and overseas. He plans to take up to $3.6 billion from the account, requiring the Pentagon to identify which projects can be delayed to free up money.

But McMahon’s promise failed to convince Democrats, who approved a resolution Tuesday to overturn the emergency declaration, which they call an unconstitutional power grab by Trump.

At one point Rep. Tim Ryan (D-Ohio) asked McMahon whether he could offer assurances that the Pentagon would not be back before Congress a year from now with another emergency request seeking money for Trump’s wall.

“Congressman, I cannot commit to you that that’s the case,” McMahon said.

“So what the hell are we here for?” Ryan asked angrily, expressing outrage over the incursion by the executive branch into Congress’s constitutional authority over federal spending.

While the Pentagon is saying the projects aren’t being canceled, it most likely won’t have enough money in its military construction account to complete them, unless Congress agrees to replenish funds taken for the wall in the coming year’s budget.

Democrats on the spending panel pointed out that a request in Trump’s budget for next year is only a request, and will not necessarily be approved by Congress. So pledging to seek replacement money for a project that has been deferred does not ensure that it will happen.

“The president’s budget request is not law,” said Rep. Sanford D. Bishop Jr. (D-Ga.).

“You are correct, and we look forward to advocating for what it is we would push for” in the next budget cycle, McMahon replied.

Senate Appropriations Committee Chairman Richard C. Shelby (R-Ala.) insisted Tuesday that Congress would act quickly to backfill funding for any affected projects, and downplayed suggestions that this would be a concern.

McMahon’s testimony came as senators are weighing how to vote on the congressional disapproval resolution to cancel Trump’s border emergency. The resolution will come up in the Senate in the next couple of weeks and will require a simple majority vote for passage.

That means only four Republican senators would need to join Democrats for the disapproval resolution to pass — and three Republicans have said they will support it.

A major concern among Republican senators, which they voiced in a private lunch Tuesday with Vice President Pence, is the risk to military construction in their states and nationwide — and the legal justification the administration is relying on to seize money that has been appropriated but not yet spent for military projects.

Several GOP senators said Wednesday they are still weighing how to vote. Sen. James Lankford (R-Okla.) said he was leaning against the resolution but was waiting for more information from the administration.

“To me it’s not just about, is it coming from my state or not, it’s the bigger issue of the legal justification,” Lankford said.

During a Senate hearing Tuesday, Sen. Tim Kaine (D-Va.) warned that if Congress allows the president to tap Pentagon funds without congressional approval whenever he decides to declare a national emergency, that would set a troubling precedent, allowing subsequent commanders in chief to take military money for any number of things by declaring an emergency.

In addition to $3.6 billion in military construction funds Trump is targeting using the national emergency declaration, he also intends to draw an addional $2.5 billion in counter-drug money from the military under authorities that don’t require an emergency declaration.

Critics have assailed the president for executing what is essentially an end-run around Congress’s constitutional power to control the appropriation of U.S. government funds.

Democrats on the Appropriations Committee accused Trump of stealing from the Pentagon budget.

“Stealing funds requested by DOD and approved by Congress and taken away from military needs, all to build his wall,” Rep. Debbie Wasserman Schultz (D-Fla.) told McMahon. “There will be real consequences for military readiness if we continue down this road.”

McMahon insisted the Pentagon would ensure that military readiness would not be jeopardized. He said the Pentagon has not yet identified projects that may be delayed to get money for the wall.

“What I do know is the president has declared a national emergency and has asked us to move forward with execution of that,” McMahon said.

The statute Trump is using to tap Pentagon funds without congressional approval stipulates that the president can do so only during a national emergency that requires the use of the armed forces and for the purposes of construction projects to support those troops. The administration will need to argue that the wall is necessary to support troops that had to be deployed to the border for an emergency — a point that has already drawn a raft of legal challenges.

To free up funds in the military construction budget, Pentagon officials have said they will be looking at delaying projects that haven’t yet been awarded, as well as those aimed at fixing or replacing existing facilities rather than building new ones. They’re also targeting projects they think are unlikely to affect the military’s readiness to fight.

Rep. John Carter (R-Tex.) asked McMahon to affirm that “you’re not going to affect readiness in any form or fashion.”

“The intent is to do exactly that, is to minimize the impact of any military construction funds that would be used and certainly not affect readiness by that,” McMahon said. “Again there are no cancellations; this is simply a deferral of capability.”

The Defense Department has ruled out taking money from military housing projects amid a scandal over poor health conditions, including vermin, lead and mold, in privatized on-base accommodations for service members.

Rep. Chellie Pingree (D-Maine) sought assurances that the decisions over what projects would be deferred would not involve political payback against lawmakers who opposed Trump’s emergency declaration. McMahon assured her they would not.

With numerous GOP senators openly skeptical about Trump’s emergency declaration, McMahon sought to reassure lawmakers that there would be no effort to scrap the projects they have pushed for and agreed to fund.

Military construction projects are a hard-fought priority for the Pentagon and for many lawmakers. Wasserman Schultz, chair of the Appropriations panel that held Wednesday’s hearing, said that there is already a $116 billion backlog of unfunded facility requirements.

The projects at risk under Trump’s emergency declaration are those that have already been approved and funded by Congress — but are not yet underway. Congressional officials have circulated a list of about $21 billion in military projects that fall in that category, spanning numerous states as well as U.S. facilities overseas. These are the projects at risk because the little-known statute the Trump administration is using to tap the military construction account limits the defense secretary to using “unobligated funds” or money that has been appropriated for certain projects but not yet spent.