WASHINGTON — President Donald Trump is using his executive authority to force defense companies to quickly produce more weaponry as his administration presses lawmakers to pass additional defense spending to replenish stockpiles depleted during the U.S.-led war with Iran.

Trump quietly invoked the Defense Production Act last week to address rising concerns within his administration about the shortfall of munitions, according to a memo filed in the Federal Register on Tuesday.

“I hereby find that conditions exist which may pose a direct threat to the national defense or its preparedness programs,” Trump wrote in a June 11 memo to Defense Secretary Pete Hegseth. Production constraints and supply chain concerns “may impair the ability of the United States to produce, sustain, and expand the availability of munitions, missiles, and equipment required for the national defense,” he wrote.

Hegseth, meanwhile, was on Capitol Hill on Tuesday meeting with Senate Republicans about a $350 billion reconciliation package for additional Pentagon funding that the administration wants them to pass, specifically to replenish munitions.

Sen. John Cornyn (R-TX) said his meeting with Hegseth ”was primarily about funding for the department” and that the Pentagon is “running short of funding they need in order to acquire the weapons and missiles and things like that that they need to protect the nation.”

The Defense Production Act is a 1950s-era law that gives the president a broad set of authorities to expand and expedite the supply of materials, including by ordering private companies to prioritize orders from the federal government. It also allows companies to collaborate in ways that could otherwise be seen as collusion or not competitive.

It is often invoked to address an emergency, including a natural disaster, a terrorist attack or a pandemic, like COVID-19.

Top administration officials have been concerned about depleting stockpiles for months, and Trump has publicly urged defense companies to manufacture more munitions. In March, just days into the war with Iran, dubbed Operation Epic Fury, NBC News reported that Trump administration officials had discussed with lawmakers the idea of invoking the Defense Production Act to accelerate the production of munitions.

Publicly, the White House insisted there are plenty of weapons.

“We have unlimited middle and upper ammunition, which is really what we’re using in this war,” Trump told reporters at the time, and a White House official later said he was referring to the range of the munitions.

Trump was expected to hold a meeting with defense industry leaders on depleting stockpile of munitions last Friday, NBC News reported, but that meeting was pushed until later this week or next due to developments in negotiations between the U.S. and Iran to end the war that were dominating his attention, according to two people familiar with the planning.

The U.S. and Iran have agreed to a Memorandum of Understanding to end the war and re-open the Strait of Hormuz while the two countries negotiate a broader deal over 60 days. The Trump administration has not released details of the MOU, though Trump has said they will be public after a signing ceremony on Friday.

Since the agreement was reached Sunday, Iran’s Islamic Revolutionary Guard Corps has fired multiple drones towards commercial ships in the Strait of Hormuz, according to a U.S. official. The official said the U.S. military has been shooting down the drones before they can threaten the commercial ships or U.S. military vessels and personnel in the region.

Hegseth has denied there is a munitions shortage, including in an interview that aired on Sunday where he said “our stockpiles are strong and they will only get stronger in the future.”

“That is a manufactured story that the media wants to peddle and ultimately our stockpiles are great, and they’re only getting stronger,” Hegseth said on CBS’ “Face the Nation.”

The defense spending package he was trying to convince Republican senators to support on Tuesday could pass without requiring votes from Democrats, according to a source with direct knowledge of Hegseth’s discussions.

Hegseth met with at least three Republicans Tuesday, including Cornyn, Senate Majority Whip John Barrasso (R-WY) and Sen. Lindsey Graham (R-SC).

Cornyn said he is supportive of the administration’s effort but is concerned Democrats would not back any new defense funding. But Democrats aren’t the only hurdle for the White House, which is preparing to submit a formal supplemental request to Congress, according to multiple senators.

Senator Lisa Murkowski, who voted several times with Democrats to try to force Trump to end the war in Iran, said while she remains open to approving funds to cover war costs, the administration needs to justify the expense.

Democrats have not ruled out supporting a supplemental funding package but are reluctant to do so while the Iran war remains unresolved and without a thorough briefing from Trump administration officials, according to a person familiar with the administration’s conversations with lawmakers.

“As long as we are at war with Iran, I will not allow a supplemental to serve as the de facto authorization for the war. And I’ve been debating this with Republican colleagues,” Sen. Chris Coons of Delaware, the top Democrat tasked with appropriating funds for the Pentagon, told NBC News in an interview last week.

Courtney Kube is a correspondent covering national security and the military for the NBC News Investigative Unit.

Julie Tsirkin is a correspondent covering Capitol Hill and the White House.

Brennan Leach is an associate producer for NBC News covering the Senate.

Kyle Stewart is a producer and off-air reporter covering Congress for NBC News, managing coverage of the House.

Carol E. Lee contributed.