The Pentagon's comptroller said it cost an extra $1.2 million to put on its portion of President Trump's "Salute to America" program for an expanded Fourth of July celebration in Washington, D.C., last week.

Defense Department officials said on Tuesday spending for personnel involvement and demonstrations largely came from their training budgets.

"The Department of Defense supported the 'Salute to America' with demonstrations by aircraft, static displays of equipment and ceremonial unit participation," the Pentagon said in its statement. "Funding for the demonstrations came from the military services' training budgets that facilitate flying hours, which are imperative to military readiness. Additional funding was used for the transportation of static displays and equipment."

White House and other Trump administration officials have remained tight-lipped in recent weeks regarding cost and other details for the event, such as how much federal agencies such as the Pentagon and the Interior Department contributed.

As a result, administration officials have faced mounting pressure and questions asking how much extra spending it cost to put on the event. The Interior Department has yet to detail its tab. NPR has reached out to the federal and local agencies involved but has not received responses yet.

Trump said on Monday he planned to repeat the salute to the military next year. The comments came on the same day a trio of Senate Democrats called for a federal watchdog to probe the event.

"It was a wonderful day for all Americans and based on its tremendous success, we're just making the decision and I think we can say we've made the decision to do it again next year, and maybe we can say, for the foreseeable future," Trump said at an event at the White House.

Less than a week after Trump led the expanded Fourth of July party in the nation's capital, Senate Democrats demanded the Government Accountability Office probe how much the final tab will cost taxpayers.

Democratic Sens. Tom Udall of New Mexico, Patrick Leahy of Vermont and Chris Van Hollen of Maryland called for a federal watchdog to dig into Trump's military tribute event on Thursday. All three are members of the Senate Appropriations Committee.

The Pentagon on Tuesday detailed the additional equipment used Thursday to execute Trump's Fourth of July vision. The flyovers included the jetliner used for Air Force One, the Navy's Blue Angels, the B-2 Spirit (also known as the Stealth Bomber), two F-35 Lightning II jets, two F-22 Raptors and two F-18 Hornets.

The aerial demonstrations also included the new helicopter that will be used as Marine One, four AH-64E Army Apache Guardian helicopters, two MV-22 Ospreys, several Coast Guard helicopters and a jet.

In all, nearly two dozen jets and helicopters representing all the military services were used, the Pentagon said. The aircraft were flown in from all over the country, including Virginia, Florida, Georgia, Missouri and California.

The Pentagon also shipped two M1A2 Abrams tanks and two M2 Bradley Fighting Vehicles more than 500 miles by rail from Fort Stewart, Ga., to Washington, D.C., to be put on display.

In addition, three military bands from the Washington, D.C., area performed at Trump's speech from the Lincoln Memorial: the Army Old Guard Fife and Drum Corps, the Marine Corps Silent Drill Platoon and the Marine Corps Band.

"The Department of Defense has a long history of showcasing military assets to the country in order to recognize our military's contributions to the safety and security of the nation, and to assist in recruiting future generations of Service members," Defense Department officials said in the Tuesday statement.

The flyovers alone were expected to cost more than $500,000, based on Defense Department flight-hour estimates. Last week, The Washington Postreported the National Park Service would shift $2.5 million in park fees to help cover the new spending.

Trump's speech was attended by military leaders, administration officials, VIPs, family and friends who obtained tickets from the White House, the Republican National Committee and the Defense Department.

Lawmakers also want the GAO to look into the event in the midst of a $12 billion maintenance backlog for the National Park Service, which is under the Interior Department. They have also raised questions about a video produced of the event tweeted by the White House and the Trump campaign.

Mark Cancian, a senior adviser with the Washington think tank Center for Strategic and International Studies, said getting a final, true tally of the extra costs for Trump's Fourth of July will be difficult.

"Some of those costs are buried in annual appropriations" for the current budget year, Cancian warned.

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