US President Donald Trump said on Sunday that the military is considering to build a large complex beneath a new ballroom being constructed at the White House, adding that details of the project had recently emerged “because of a stupid lawsuit".

According to AFP, Trump, who was aboard Air Force One, stated, “The military is building a massive complex under the ballroom, and that's under construction, and we're doing very well, so we're ahead of schedule. It's part of it, the ballroom essentially becomes a shed for what's being built under.”

Trump said last week that the ballroom project included a national security component that was originally intended to remain confidential, reported The Hill. Speaking at a Cabinet meeting on Thursday, he added that the military had strongly supported the project, but the details were no longer secret. He alleged that the information had been made public by individuals he described as unpatriotic.

Trump has often spoken at length about the project, which has so far moved ahead without the typically complex approval processes required for alterations to Washington’s architectural landscape.

“We are using onyx and other remarkable stones,” he recently said at a press conference that partly focused on the Middle East conflict.

The ballroom project, one of the most undertakings at the White House in more than a century, has expanded significantly, with its privately funded budget rising from $200 million to $400 million.

Last October, the former real estate developer had an entire wing of the White House demolished to make way for a massive ballroom intended for hosting receptions and state dinners.

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Keen to make a lasting imprint on the US capital, Trump has also renamed a prominent performance venue the “Trump-Kennedy Center” and is planning to construct a grand arch in Washington modeled on Paris’s Arc de Triomphe.

White House ballroom project details Trump said last summer that he intended to build a ballroom at the White House, saying there was a need for a permanent venue to host key guests instead of relying on a temporary tent on the lawn. In October, the East Wing was demolished with little prior notice, and groundwork beneath the site has been underway since then. Officials have indicated that construction above ground is unlikely to begin before April.

The National Trust for Historic Preservation, a private nonprofit organisation, moved a federal court seeking a temporary pause on the project, arguing that the White House should first present its plans to federal review bodies and Congress, and allow public input. However, US District Judge Richard Leon dismissed the request, with the Trust saying it plans to file a revised lawsuit, according to AP.

David Scott Parker, a Fellow of the American Institute of Architects whose firm specialises in residential design and historic preservation, based his review on design renderings and other materials submitted by the White House to the Commission of Fine Arts last month, reported AP. He pointed out that the ballroom would occupy about 22,000 square feet (2,043 square metres), which he said is significantly larger than required for the 1,000 guests Trump expects it to host.

According to industry norms of roughly 15 square feet (1.4 square metres) per person, Parker said the space could be reduced by about 47% to around 15,000 square feet (1,394 square metres).

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The design also includes a 4,000-square-foot (372 square metres) south-facing porch and staircase. Parker argued these features are unnecessary, as they do not provide direct access to the building’s interior, and added that the porch fails to meet requirements under the Americans with Disabilities Act.

The White House said the ballroom would comply with federal accessibility laws, though it did not directly address Parker’s criticisms. The proposed portico is also much larger than those on the south side of the White House and the nearby Treasury Department building.

Concerns over the scale of the project have persisted since the outset. At nearly double the size of the main White House building, which spans about 55,000 square feet (5,110 square metres), critics argue the addition could dominate the historic structure and disrupt the overall symmetry of the complex.