WASHINGTON — A new National Park Service report backs President Donald Trump’s proposed arch, despite what it says are adverse effects to the sightline between a host of iconic landmarks in Washington, including the Washington Monument and Lincoln and Jefferson memorials.

The report released Friday says the 250-foot-tall (76-meter) memorial arch is likely to disrupt the historical significance of dozens of sites near its planned location adjacent to Memorial Bridge.

Many of Washington’s monuments, buildings and sites have been carefully planned over decades to reflect significant moments in the nation’s history and to evoke symbolism through sightlines that connect them to other sites. The arch will disturb the sightline between more iconic Washington landmarks than anticipated, the report said.

But the Park Service report says “the same characteristics that make Memorial Circle sensitive from a preservation perspective are also the characteristics that make it the historically appropriate location for the undertaking.”

The project’s effects cannot be “fully avoided without either relocating the Arch away from the historically identified site or eliminating the principal commemorative feature, both of which would fail to meet the undertaking’s purpose and need,” the report said.

“For this reason, alternative locations outside Memorial Circle are not reasonable avoidance alternatives,” the report said.

The 133-page report by the Park Service supports Trump’s plans for the controversial arch and could play an important role in bolstering the administration’s case in its fight against a legal challenge filed by three veterans and a group of historians.

The proposed towering gilded arch, which last month received initial approval from a key federal commission, would impact the “integrity” of dozens of historic properties because it would change “character-defining visual and spatial relationships” between them.

One of the most obvious elements the report cited is that the arch would break alignment between the Lincoln Memorial, Memorial Bridge and Arlington House that was formerly Confederate Gen. Robert E. Lee’s home. That alignment was “intended to physically and symbolically unite North and South through a coordinated monumental composition extending across the Potomac River,” the report said.

The Lincoln Memorial Arlington House connection was one of dozens of historic sites and structures listed as being impacted directly by the proposed structure. It added that the National Mall, the U.S. Capitol, Washington Monument, Jefferson Memorial, Georgetown Historic District, Old Naval Observatory, Key Bridge, National Cathedral and other sites also would be affected.

Nicolas Sansone, an attorney with Public Citizen Litigation Group representing the plaintiffs, said the report again “confirms what we’ve been saying all along: the project will have an enormous impact and transform that National Mall.”

The report underscores the legal challengers’ claim that a project of this size and importance “is a decision for Congress to make” and should not be rushed through by executive decree, Sansone said.