DETROIT — General Motors has built one of the most exclusive, impenetrable and expensive cars in the world to transport the most important person in the free world.

The Secret Service will give up a little info, but the company won't talk about it.

"We cannot comment on this," Cadillac spokesman Andrew Lipman wrote in an email.

So what's the big secret? It's President Donald Trump's new limousine that Cadillac built, called "The Beast."

The U.S. Secret Service, in an email to the Detroit Free Press, confirmed that on Sept. 17, a new armored limousine made its debut in the presidential limo fleet. An agent confirmed the 2018 custom-built Cadillac is in use in New York City this week, shuttling Trump around as he attends United Nations General Assembly meetings. It has a twin version that travels in Trump's motorcade.

The Secret Service posted a photo on Monday of two new limousines on Twitter with the line, "The Secret Service is ready to roll into #UNGA 2018!" the agency wrote.

"This vehicle, a 2018 Cadillac, continues the Secret Service’s legacy of providing state-of-the-art technology and performance to its protective mission," Jeffrey Adams, special agent and spokesman for the Secret Service, said in the email.

GM won contracts worth $15.8 million for two phases of the development of the limo from 2014 through 2017, Reuters reported, citing federal contracting records. It said it is not clear if that figure includes all the costs, noting that in 2010, GM won a $35 million contract from the Secret Service for more presidential limousines.

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It first won the contract for the new limo in 2014 after Ford opted to not bid, Reuters said. Since the early 1980s, the presidential limo has been a Cadillac, but prior to that it was a Lincoln.

The previous version of the presidential limo debuted in January 2009 ahead of Barack Obama taking office. In a 2015 episode of "Comedians in Cars Getting Coffee," Obama told Jerry Seinfeld it was "a Caddy basically on a tank frame."

Obama went on to tell Seinfeld that he could phone "a nuclear submarine" from the car, and joked that its best feature was the seat warmers.

The limo can hold about 10 people, but surprisingly, don't expect leather seats for the president. The president's bench is covered in a dark blue cloth, said published reports. A folding desk separates the president from a companion's seat.

Here is what else makes it extra cool:

The exterior armor plating is reportedly 8 inches thick, making its doors weigh the same as those on a Boeing 757 aircraft. Its bulletproof windows are 5 inches thick and its nearly bus-size tires can run-flat to keep The Beast in motion for some distance if needed, reports say. The interior is completely sealed to protect occupants against a chemical attack. There is even a special foam that would surround the fuel tank to shield it during an impact. And, as Obama told Seinfeld, it has extensive electronic communications equipment too, reports said.

One more thing, it gets its own airplane. The Secret Service uses a C-17 Globemaster transport aircraft to fly The Beast, a second limo and a heavily armored Chevrolet Suburban communications SUV, dubbed Roadrunner, to any where the president is traveling. Roadrunner is reported to be a communications office on wheels that is directly linked to a military satellite.

Contact Jamie L. LaReau at 313-222-2149 or jlareau@freepress.com