US President Donald Trump on Tuesday revealed previously undisclosed details about his new bunker-like White House ballroom, saying it would have a drone base on ​the roof and a military hospital as part of a six-story subterranean complex.

Amid ‌the bang and clang of construction, Trump took a group of reporters on a tour of the project to try to bolster his argument that the US Congress should allocate $1 billion to pay for security enhancements to the building.

Democrats ​and some Republicans are baulking at the request, calling it extravagant as Americans grapple with ​spiralling gasoline prices and other fallout from Trump’s war on Iran ahead of the November ⁠midterm elections.

Trump, a billionaire real estate developer, did not hold back in describing previously unknown ​details about the project, which at 90,000 square feet stands to dwarf the adjacent White House, built ​in the late 18th century.

Trump has argued that the ballroom is needed for large events of 1,000 people, far more capacity than the White House entertainment spaces can accommodate.

He pressed his case for the ballroom after an apparent ​assassination attempt at a Washington hotel where he was attending a media gala, arguing that it would ​be a much more secure venue.

Trump detailed the ballroom’s security features, describing a bunker-like structure with a hardened roof ‌able ⁠to withstand a direct attack.

He said the titanium fencing recently installed around the ballroom was so strong that “a bulldozer cannot knock it over.” The roof, he said, would be constructed of “impenetrable steel.”

Beneath the ballroom, there will be a complex extending six stories deep, he said, pointing to two that were already ​under construction.

The underground complex ​would include a military ⁠hospital and research facilities, although Trump did not explain the focus of the research. The White House declined to provide further details.

He spoke excitedly about ​the installation of a drone base on the roof, “set up for unlimited numbers ​of drones.”

“The ⁠entire roof is built for military,” he said. “They have a massive drone capacity. Not only is it drone-proof; if a drone hits it, it also bounces off, and it won’t have any impact. But it’s also meant ⁠as a ​drone port that would protect all of Washington.”

The ballroom’s ​windows would be four inches thick and made from a special kind of glass.

“You can see through it as though it ​doesn’t exist,” he said.