A US judge ruled on Tuesday that President Donald Trump cannot build a ballroom on White House grounds without congressional approval.

Trump's $400 million (€346 million) ballroom was planned for the White House's East Wing, which was demolished last year to make way for the new structure.

The US president has said the ballroom is a necessary addition to the White House complex.

The nonprofit organization National Trust for Historic Preservation brought the lawsuit to federal court, alleging that Trump had exceeded his authority with the project.

US District ⁠Judge ⁠Richard Leon, an appointee of Republican former President George W. Bush, granted a request for a preliminary injunction, which would put the construction of the ballroom project on hold until the legal matter can be resolved.

"The President of the United States is the steward of ⁠the White House for future generations of First Families. He is not, however, the owner!" Leon wrote in the court order.

"Where does this leave us? Unfortunately for Defendants, unless and until Congress blesses this project through statutory authorization, construction has to stop!" he added.

'Left wing lunatics'

The Trump administration was given 14 days to appeal the decision, which it filed right away, shortly after the ruling came out.

"This is a win for the American people on a project that forever impacts one of the most beloved and iconic places in our nation," the preservation group's CEO Carol Quillen said in a statement. 

Trump has hit back at the National Trust for its legal challenge against his ballroom.

In a post on his social media site Truth Social, he referred to the National Trust as a group of left-wing "lunatics" and defended his ballroom as "under budget, ‌ahead of schedule, being built at no cost to the Taxpayer, and will be the finest Building of its kind anywhere ‌in the World."

The group has also brought up a legal challenge against the Trump administration over its move to overhaul the Kennedy Center performing arts venue in Washington, a place that Trump unilaterally renamed as the Trump Kennedy Center.

Edited by: Srinivas Mazumdaru