A US judge has temporarily halted President Donald Trump's White House ballroom construction project, ruling that proper procedures were not followed before the project began.

The decision comes after the White House was sued by the National Trust for Historic Preservation.

I have concluded that the National Trust is likely to succeed on the merits because no statute comes close to giving the President the authority he claims to have, said Judge Richard Leon.

Trump criticized the ruling on his social media platform, saying the project is going well, and will be the finest Building of its kind anywhere in the World.

The Trump administration previously stated that its plan was more economical than renovating the East Wing and noted that many presidents have made changes to the White House.

Leon's ruling, published on Tuesday, continued: 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!

(U)nless and until Congress blesses this project through statutory authorization, construction has to stop! added the judge, who was appointed by President George W Bush.

The 35-page ruling uses a large number of exclamation points, emphasizing that Congress must approve the project before it can resume.

The order will take effect in 14 days, allowing for a possible appeal.

In the lawsuit, the preservation group argued that the White House broke the law by beginning construction without filing plans with the National Capital Planning Commission, omitting an environmental assessment of the project, and failing to seek authorization from Congress. It also alleged Trump was violating the US Constitution, which reserves to Congress the right to dispose of and make all rules regarding property belonging to the United States.

In his conclusion, Leon wrote that with White House approval from Congress, the American people will benefit from the branches of Government exercising their constitutionally prescribed roles.

Not a bad outcome, that! added the judge.

The East Wing, which was constructed in 1902, was demolished last October to make way for Trump's multi-million dollar ballroom, which originally was proposed to accommodate 500 people but has since expanded to fit up to 1,350 guests.

The White House estimates the project will cost $400 million, funded entirely by private donors.

The National Trust's president, Carol Quillen, expressed satisfaction with Judge Leon's ruling, stating: 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.

Reacting to the judge's decision, Trump asserted that the ballroom was under budget, ahead of schedule, and will be the finest of its kind, also criticizing the trust for suing to halt renovations of the Kennedy Center.

In his remarks, Trump denied needing Congress's approval to continue constructing the ballroom and emphasized the importance of building a suitable venue for the forthcoming visit of King Charles III.

The construction already has progressed, with demolition completed; however, the judge's order may put a pause on future work.