President Donald Trump said he is moving forward with the construction of a large new ballroom complex at the White House, emphasizing that it's "too late" to go back, even as the project faces a legal challenge from historic preservation advocates.

In a statement, Trump said the ballroom — which he called one of the largest and most elaborate of its kind in the world — will cost between $300 million and $400 million but that it will be funded entirely with private money, not taxpayer dollars. 

He said the project is being developed in coordination with the U.S. military and the Secret Service and is intended to provide a permanent, secure venue for major state events, including dinners, conferences and future presidential inaugurations.

According to Trump, the White House has long relied on temporary tents erected on the South Lawn for large gatherings, which he characterized as unsafe, weather-dependent and inadequate for modern security needs. He said previous administrations had sought a permanent solution for more than a century without success.

The project has drawn opposition from the National Trust for Historic Preservation, which has filed a lawsuit seeking to block construction. Trump strongly criticized the group, accusing it of obstruction and questioning its motives. 

"All of the Structural Steel, Windows, Doors, A.C./Heating Equipment, Marble, Stone, Precast Concrete, Bulletproof Windows and Glass, Anti-Drone Roofing, and much more, has been ordered (or is ready to be), and there is no practical or reasonable way to go back. IT IS TOO LATE! Why didn’t these obstructionists and troublemakers bring their baseless lawsuit much earlier?" Trump wrote on Truth Social.

"Congress never tried, or wanted, to stop the Ballroom Project! Everyone knew what was taking place at the White House — A great, big, beautiful gift to the United States of America! For those that are interested, the tiny East Wing was so 'bastardized' and changed, built and rebuilt over the years, that it bore no resemblance or relationship to the original building," he added.

Trump also said the National Trust for Historic Preservation should not be allowed to halt the project.

"The so-called 'preservationists,' who get their money from the most unusual of places, should not be allowed to stop this desperately needed addition to our GREAT White House, a place that a President has never needed permission to change or enhance, because of the special grounds on which it sits, no matter how big (and important!), that enhancement may be," he said. 

Trump said the ballroom is being done with the design, consent, and approval of the "highest levels" of the U.S. military and Secret Service. 

"The mere bringing of this ridiculous lawsuit has already, unfortunately, exposed this heretofore Top Secret fact. Stoppage of construction, at this late date, when so much has already been ordered and done, would be devastating to the White House, our Country, and all concerned," he wrote.