LET’S SAY you own a large luxury hotel on Pennsylvania Avenue near the White House. It’s a good bet the last thing you want is another hotel opening across the street.

In this case, the owner of the luxury hotel happens to be the president of the United States, and the competition he is unlikely to want is the prospect of a new hotel built on the existing site of the J. Edgar Hoover building — the hulking, crumbling headquarters of the FBI that sits catty-corner from the Trump International Hotel. The fact of that proximity, and the apparent conflict between Mr. Trump’s private business interests and the public’s interests, may be why the FBI remains stuck in an inadequate and obsolete building.

A year ago, the Trump administration, citing uncertain funding, abruptly scrapped a plan to shift the FBI to a modern, CIA-style campus in the suburbs, a move that would consolidate thousands of bureau employees now scattered among the Hoover building and more than a dozen other locations around the Washington area. The cancellation after a decade of planning and nearly $1 billion of appropriations by Congress shocked state and local officials and the four developers who were finalists in bidding for the project. It took place practically on the eve of a decision to select the developer who would raze the existing headquarters and redevelop it, as part of a deal to also build the FBI’s new suburban complex.

Mr. Trump’s interest in the FBI project pre-dates his presidency — in 2013, he told The Post that he was considering bidding on the deal. Now, it turns out his personal intervention may be instrumental in the ongoing paralysis. Axios reports that the president is “dead opposed” to transferring the headquarters out of Washington. The Post’s Jonathan O’Connell reported that the decision not to relocate the headquarters, but instead to raze and rebuild a still-too-small one on the existing site, came after Mr. Trump got personally involved.

The White House, citing Mr. Trump’s background in commercial real estate, said the president wants to ensure funds for a new building are spent “wisely and appropriately.” But it’s hard to see how building a new FBI headquarters on the existing site would be wise or appropriate. It is too small to accommodate the FBI’s 11,000 headquarters staff and would require shifting some 2,300 of them to sites in Idaho, Alabama and West Virginia . Rebuilding on the existing site would also preclude features long deemed priorities, including a separate facility for inspecting trucks and a detached utility plant. And no one has calculated the cost of moving 5,000-some employees out of the Hoover building during construction, then back again years later to a new edifice.

Unsurprisingly, the administration’s proposal has attracted little support and no funding. The Hoover building, plagued by crumbling concrete that poses a risk to pedestrians below, inadequate security and outdated systems, isn’t getting any younger. That may be just fine with Mr. Trump; it’s not so good for the nation.

Read more:

Richard Cohen: Tear down J. Edgar Hoover’s name

Gerry Connolly: The retreat on the FBI building is a farce within a farce

The Post’s View: Practicality — not politics — is what’s important in choosing the new FBI headquarters

The Post’s View: The cancellation of a new FBI headquarters is illogical and embarrassing

Martin Austermuhle: D.C.’s world-class eyesore