President Donald Trump’s proposed 76m triumphal arch in Washington won a key approval late on Thursday, which could lead to construction beginning quickly on the latest major project in his drive to reshape the US capital.

The National Capital Planning Commission voted to approve the project after hearing from about 100 opponents, including Democratic legislators.

“It will snarl traffic for years, impact the nearby airport, and present even more serious threats to public safety that this commission has refused to acknowledge and grapple with,” said representative Don Beyer, who represents northern Virginia.

A judge considering several legal challenges could still block the start of construction. But if it gets the go-ahead, the justice department has said it expects an initial six to eight months of construction focused on excavation and foundation work could begin this week.

Above ground construction would start in May 2027 at the earliest, with the job expected to take 33-39 months in total.

The National Park Service may also issue a permit or other authorisation on Thursday and launch construction this week, the government said in a court filing.

The arch is among several costly projects Trump is pushing in Washington despite opposition from local officials and preservationists. They include rebuilding the Reflecting Pool at the Lincoln Memorial, constructing a massive White House ballroom and overhauling the Kennedy Centre for the Performing Arts.

The arch has faced significant opposition in the courts. The state of Virginia and the District of Columbia sued the National Park Service and the department of the interior on Saturday, seeking to halt the start of construction, calling it “legally indefensible” and arguing that Congress has not approved it.

It’s right smack in the middle of everything, so very important for our military. But from a beautification standpoint, it’ll be the most beautiful arch in the world

The government contends Congress approved the arch more than 100 years ago when it also authorised construction of a bridge across the Potomac River.