WASHINGTON (AFP)

US President Donald Trump on Tuesday showed off the site of his huge new White House ballroom.

The billionaire property magnate took reporters to see the construction work, speaking above the sounds of hammering, sawing and clanging.

“This is a gift to the United States of America,” said Trump, standing by yellow railings on the edge of a cavernous concrete basement space. "This is all my money and donors' money. This is tax free."

Trump went into detail about what he said were the security aspects of the ballroom project, saying there were six stores below ground that would house military installations, research facilities, and even a hospital.

“The ballroom becomes a shield that will totally protect what's going on downstairs,” 79-year-old Trump said.

He added that drones would "bounce" off the roof of the ballroom and said it would be a good site for snipers.

The property developer in Trump was also in full display, as he talked about how one facade of the ballroom was styled after ancient Greece, and another after Rome.

Trump has repeatedly said the ballroom -- whose cost has doubled from an initial estimate of $200 million -- is being met by private donors, including his wealthy supporters and a slew of corporations.