The Trump administration plans to break ground on its proposed 250-foot arch near Washington, D.C.'s National Mall in the coming days, without key approvals and despite an ongoing lawsuit.

Interior Secretary Doug Burgum wrote on social media Thursday that "we are preparing to start, over the next two-week period, the excavation work necessary for the Great Triumphal Arch and Military Observation Deck."

But the arch is still awaiting final approval from the National Capital Planning Commission, as well as federally mandated reviews regarding aviation safety and historic preservation.

Historic preservation experts have long criticized the Trump administration for seeming to rush the arch approval process, including by moving to weaken protections for historic sites altogether. This latest development raises concerns that the White House seeks to sidestep the process, which it denies.

"Work will begin that does not require approval, but rather helps in the process," the White House told NPR in a statement on Friday. "We will of course continue on our path of seeking final approval from all applicable entities."

The White House, Department of the Interior and National Park Service did not respond to NPR's questions about the timeline and extent of the excavations or the addition of the word "military" to the structure's title.

President Trump told journalists last year that the arch is for "me." But since then, the administration has said the arch is intended to honor the nation's 250th anniversary

"This will be one of the Great Pieces of American Architecture, honoring the history and significance of Arlington Cemetery and befitting the most powerful Capital in the World," Burgum posted this week, alongside renderings of the white-and-gold structure, topped with three large gilded statues.

The arch has been controversial since its inception, greenlit by federal panels packed with Trump allies despite unanswered questions, thousands of overwhelmingly negative public comments and an ongoing lawsuit.

An architectural historian and three Vietnam War veterans, working with the nonprofit Public Citizen, sued to stop construction earlier this year. They argue the arch would desecrate Arlington National Cemetery and requires congressional approval, which Trump denies and has not sought.