President Donald Trump said on Friday he would appeal to the U.S. Supreme Court over a lower court’s decision to stop construction on a $400 million ballroom at the White House complex.

“The decision has been stayed, and does not take effect for a period of time. We will be immediately appealing to the United States Supreme Court,” Trump wrote in a social media post. “This unjust decision must be overturned by the Supreme Court in its entirety.”

A U.S. federal appeals court earlier on Friday ordered Trump’s administration to stop construction on the ballroom on the site of the White House’s demolished East Wing, dealing the Republican leader a major setback in a case testing his presidential authority.

The Washington-based U.S. Court of Appeals for the District of Columbia Circuit in a divided 2-1 order upheld a preliminary injunction won by the National Trust for Historic Preservation, which sued last year after the administration tore down the East Wing and began building a 90,000-square-foot (8,360-square-meter) ballroom without seeking authorization from Congress.

“Whether or not a massive ballroom should be constructed is for Congress to decide and is not a matter for Executive self-help,” the panel’s majority wrote. “Congress has not ceded unfettered authority to the Executive Branch to dramatically redesign, reshape, and reconstruct the White House — the People’s House — to fit a particular President’s desires.”

The appeals court placed its ruling on hold for 14 days to allow the Trump administration to appeal to the U.S. Supreme Court.

The White House and Justice Department did not immediately respond to requests for comment.

Trump appealed after U.S. District Judge Richard Leon twice blocked above-ground construction on the site while allowing underground work to continue.

Leon, an appointee of Republican former President George W. Bush, had ruled that no federal statute “comes close to giving the President” the required ​authority to construct the ballroom without ​congressional approval.

The ballroom plan, which the administration has described as necessary for large formal functions and to preserve the safety of the White House, is the grandest of several Trump efforts to reshape central Washington’s landscape of government buildings and national monuments.

A judge in a separate lawsuit recently said Trump’s name was illegally added to the exterior of the Kennedy Center performing arts center and ordered its removal.

In the ballroom case, Justice Department attorney Yaakov Roth said during D.C. Circuit arguments on June 5 that the courts have no role in weighing the privately funded project and that it would have been improper to block it at any point.

Roth said the National Trust’s “architectural preference” against the ballroom shouldn’t take precedence over national security concerns, claiming evidence that the former East Wing left the president and others in the White House vulnerable to attack.

“They ⁠just don’t want to go to Congress,” countered Thaddeus Heuer, a lawyer for the preservation group.

Trump has defended his ballroom and its price tag, which has doubled from initial projections. Trump said in a post on Truth Social last month that the cost rose because “it is approximately twice the ​size, and a far higher quality, than the original ⁠proposal” and promised “it will be magnificent, safe, and secure!”