Roughly $2.5 million allocated for the National Park Service will be diverted to fund President Donald Trump's "Salute to America" Fourth of July celebration, two unnamed sources familiar with the matter told The Washington Post.

The funds were reportedly diverted from entrance and recreation fees generated by the National Park Service.

Lawmakers and former White House officials have criticized the event for its cost and optics.

Military vehicles have been spotted being freighted in by railroad cars from Fort Stewart, Georgia, and are expected to move through the city Tuesday evening.

"You'll see them moving through your neighborhood, but don't panic," a US Army spokesperson said to WUSA.

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Roughly $2.5 million allocated for the National Park Service will be diverted to fund President Donald Trump's "Salute to America" Fourth of July celebration, two unnamed sources familiar with the matter said, according to a Washington Post report published on Tuesday.

The funds were diverted from entrance and recreation fees generated by the National Park Service, according to The Post. Denis Galvin, a former park service deputy director, told The Post that the Fourth of July celebrations at the National Mall in Washington, DC, normally cost the park service about $2 million.

The park service cares for over 400 parks and 60 rivers throughout the country. The agency asked for $2.4 billion in its total 2020 budget request.

The total cost of Trump's parade is expected to exceed previous Fourth of July celebrations. Unlike previous celebrations, Trump's version is expected to consist of fighter-jet flyovers, helicopters, and armored vehicles — including two M1 Abrams tanks.

"We have some incredible equipment, military equipment, on display — brand new," Trump said on Monday. "We're going to have a great Fourth of July in Washington, DC. It'll be like no other."

Read more: Here's all the military firepower Trump wants to show off at his big Fourth of July bash

Lawmakers and former White House officials criticized the event for its cost and optics. Trump has been accused of politicizing the military and using its assets to boost his political standing as the 2020 US presidential election looms near.

It is unclear what the overall cost of the event will run American taxpayers. Trump's scuttled parade in November — which was expected to include extravagant displays of the military's assets — was estimated to cost $92 million.

The Department of the Interior, which operates the National Park Service, did not respond to requests for comment.

"It is unacceptable that the Interior Department is failing to inform Congress about how it plans to spend taxpayer money to fund the president's lavish July 4th plans, which reportedly include special access to the National Mall for the politically connected," Democratic Sen. Tom Udall of New Mexico said in a statement. "The American people deserve to know how much of their money the president is spending to turn their July 4th celebration into a de facto campaign rally."

"All reports indicate that the president is planning to turn a national day of unity into a day of vanity — trying to use the military for political purposes and doling out perks to his political backers — at the taxpayers' expense," Udall added. "We need answers."

Former Defense Secretary Leon Panetta described the celebration as an unnecessary display of military might — similar to that of the US's foreign adversaries.

"I don't think it is in keeping with what our country is all about," Panetta said to CNN on Tuesday. "We're the strongest military power on the face of the Earth. And we have never had to display that power to the world in order to prove it. We know who we are. We know our strengths."

The military's preparations for the event are already underway in Washington, DC, despite the concerns. Military vehicles have been spotted being freighted in by railroad cars from Fort Stewart, Georgia, and are expected to move through the city Tuesday evening.

"You'll see them moving through your neighborhood, but don't panic," a US Army spokesperson said to WUSA.