Fifty of the country's top Republican national security officials have signed a letter saying they do not support their party's presidential nominee, Donald Trump.

The New York Times first reported the letter, which was signed by people who worked under Republican administrations from Richard Nixon to George W. Bush. Those signing the letter include former Director of National Intelligence John Negroponte, former NSA and CIA Director Michael Hayden and former Homeland Security Security secretaries Michael Chertoff and Tom Ridge.

Trump, the letter writers argue, "would be the most reckless president in American history."

"None of us will vote for Donald Trump," they say, though they acknowledge that many Americans have concerns with the Democratic nominee Hillary Clinton, as well.

According to the letter, Trump has "demonstrated repeatedly that he has little understanding of America's vital national interests" and "its complex diplomatic challenges. Unlike previous presidents," they say, "Mr. Trump has shown no interest in educating himself."

Trump "is unable or unwilling to separate truth from falsehood," the letter says. "He does not encourage conflicting views. He lacks self-control and acts impetuously. He cannot tolerate personal criticism. He has alarmed our closest allies with his erratic behavior."

Late Monday afternoon, Trump issued a response to the letter. His statement said that “the names on this letter are the ones the American people should look to for answers on why the world is a mess.”

He called them part of the failed elite who need to be told “their gravy train is over.”

Trump on former nat sec leaders who wrote scathing letter: "They are nothing more than the failed Washington elite" https://t.co/1xONEr5BTG — Jim Acosta (@Acosta) August 8, 2016





“These insiders – along with Hillary Clinton – are the owners of the disastrous decisions to invade Iraq, allow Americans to die in Benghazi, and they are the ones who allowed the rise of [the Islamic State in Iraq and Syria],” Trump continued.

“Yet despite these failures, they think they are entitled to use their favor-trading to land taxpayer-funded government contracts and speaking fees,” Trump added.

“It’s time we put our foot down and declare that their gravy train is over: No longer will Crooked Hillary Clinton and the other disasters in Washington get rich at our expense.”

The Times notes that some prominent Republican national security officials did not sign the letter, including former secretaries of state Henry Kissinger, George Shultz, James Baker, Colin Powell and Condoleezza Rice.

Trump has met with Kissinger and Baker in recent weeks, though neither have endorsed him.

Trump surrogate Dr. Ben Carson, who was a Trump challenger for the GOP nomination, told CNN on Monday that Trump and "a lot of the American people" recognize the letter's signatories are the very people who have been running things and "have kind of run us into the ditch."

"If things aren't moving in the right direction, you analyze it and move into a different direction," Carson said, adding that establishment members of both parties have been responsible for decades of bad policy that have gotten America into its current condition.

"People must get that through their thick skulls," he said. "We must understand that our strength is in our unity and resist the urge to capitulate to those agents of the vision who derive their power and their power base from the dividing people into groups."