The District of Columbia and Virginia sued the Trump administration Saturday to block construction of President Donald Trump's proposed 250-foot triumphal arch near Arlington National Cemetery.

The joint lawsuit, filed in federal court in Washington, describes the project as "flagrantly unlawful" and argues it lacks required congressional authorization under the Commemorative Works Act. It also claims the structure would violate the Height of Buildings Act, which generally limits structures in the capital to 130 feet.

Attorneys General Brian Schwalb of D.C. and Jay Jones of Virginia said the arch would cause immediate and irreparable harm through traffic disruptions, environmental damage, and impacts on security and emergency preparedness. The site at Memorial Circle sits on a key traffic artery between the jurisdictions.

Construction could begin as early as next week if the National Capital Planning Commission grants final approval, according to court filings. The administration has defended the project as a commemoration of the nation's 250th anniversary and, in some statements, as serving national security purposes.

This marks the latest in a series of legal challenges. Arlington County sued earlier this month over environmental review concerns, and a group of Vietnam War veterans has also filed suit, citing blocked views of the cemetery from the Lincoln Memorial.

The new case has been assigned to U.S. District Judge Tanya Chutkan, who is already considering a related request for an injunction. Plaintiffs seek a temporary restraining order to prevent any groundbreaking.

Trump has promoted the arch as a major addition to the capital's landscape. Opponents, including the Democratic attorneys general, have labeled it a vanity project that bypasses standard federal review processes under environmental and historic preservation laws.