The U.S. Department of Justice has intervened in the high-profile legal battle over President Donald Trump’s planned White House ballroom expansion, arguing that a judge should preserve ongoing construction on national security grounds.

In a court filing submitted this week, the DOJ asked a federal judge to stay any potential injunction blocking the project, asserting that pausing work could imperil the safety and security of the president and others at the executive mansion.

The filing, entered before the end of the business day on Monday, came ahead of a decision by U.S. District Judge Richard Leon on whether to halt construction while litigation proceeds.

Lawyers for the government described the ballroom project, which includes demolition of the White House’s historic East Wing, as “imperative for reasons of national security” and warned that leaving the site in its current condition would create security vulnerabilities and complicate operations by the U.S. Secret Service, the agency tasked with protecting the president.

In supporting their position, DOJ attorneys cited an attestation from a senior Secret Service official indicating that an open excavation area in President’s Park poses a hazard and could hamper protective operations if work is abruptly stopped.

The administration also signalled its intent to file a second, classified declaration from the Secret Service to further explain the national security implications of halting construction, offering to present it to the judge ex parte if necessary.

The legal dispute was triggered by a lawsuit from the National Trust for Historic Preservation, which seeks to block or delay the ballroom project on the grounds that the administration failed to comply with procedural requirements including independent historic and environmental reviews and congressional authorization.

Judge Leon has expressed scepticism about the administration’s broader legal authority to undertake the project without such oversight, and he has scheduled additional hearings to consider the preliminary injunction request.

In its latest filing, the DOJ argued that the U.S. Court of Appeals for the District of Columbia Circuit should weigh in on the novel legal questions before any order is issued that could force a work stoppage in the midst of a project it says implicates fundamental security considerations.

The filing reiterated that distinguishing between security-related and other elements of the construction would be “unworkable,” underlining the administration’s position that continuity of work is essential for protective needs.