The federal commission reviewing President Donald Trump's planned 250-foot triumphal arch kept the project alive Thursday while its Trump-appointed chairman, Will Scharf, told a public hearing he does not believe the 1910 Height of Buildings Act constrains federal construction in Washington, the threshold legal question hanging over a monument that would rise to more than 2.5 times the height of the nearby Lincoln Memorial.

The National Capital Planning Commission, which has long applied the Height Act's 130-foot cap to projects in the capital, voted to seek further information from the Interior Department rather than reject or finally approve the arch, leaving the dispute over the statute's reach unresolved.

The administration says it does not need congressional authorization and will give at least 14 days' notice before breaking ground.

Scharf, who also serves as Trump's staff secretary, told commissioners he had "thought deeply" about the act's reach and concluded that "the best reading of the law is that the Height of Buildings Act is not applicable to federal construction."

He argued that the commission's longstanding contrary position struck him as "a little odd" from a legal perspective and runs counter to the separation of powers, citing federal structures that exceed the cap, including the National Archives building, which the Washington Post reported stands at 166 feet.

Enacted by Congress in 1910, the law generally caps commercial-street buildings at 130 feet, with a carve-out permitting 160 feet along stretches of Pennsylvania Avenue NW.

Career NCPC staff, in a report issued before the hearing, noted the agency "has always applied the Height of Buildings Act to federal projects" and asked Interior to justify the arch in light of the cap.

Designed by classical architect Nicolas Leo Charbonneau of Harrison Design and steered by the Interior Department, the arch would rise in Memorial Circle, the traffic roundabout where Arlington Memorial Bridge meets the District.

Interior is consulting with the Federal Aviation Administration on potential hazards to Reagan National Airport.

The Commission of Fine Arts, which contains Trump appointees, signed off on the design last month.

The project drew sharp pushback at Thursday's hearing.

Carol Quillen, chief executive of the National Trust for Historic Preservation, told the panel the arch is "inconsistent with the Height of Buildings Act that protects the plan of the city."

Her organization is already suing the administration over Trump's planned White House ballroom.

A separate suit by three Vietnam War veterans, filed in February in the U.S. District Court for the District of Columbia, contends the arch requires congressional approval and would mar sightlines between the Lincoln Memorial and Arlington National Cemetery.

Public sentiment runs against the project.

Some 52% of Americans oppose the arch and 21% support it, with 41% strongly opposed, according to an ABC News-Washington Post-Ipsos poll conducted online April 24-28 via the probability-based Ipsos KnowledgePanel, weighted to U.S. adult population benchmarks.

The arch question was asked of a random half-sample of 1,292 adults, with a sampling error margin of plus or minus 2.8 percentage points.