(CNN)A group of leaders in the Republican foreign policy and national security community wrote an open letter condemning Donald Trump and pledging to oppose his presidential candidacy.
GOP ex-national security officials: Say no to Trump
"We are unable to support a Party ticket with Mr. Trump at its head," they wrote in the letter, first posted Wednesday night on the website warontherocks.com.
Trump dismissed the letter -- as well as comments by former director of the National Security Agency Michael Hayden who said if Trump ordered torture, the military would disobey him.
"I'm a leader. I don't think that would happen. They're cutting off heads in the Middle East. They're chopping off people's heads in the Middle East and we're afraid to waterboard," the Republican front-runner said Thursday on ABC's "Good Morning America." "Give me a break. Gen. Douglas MacArthur and Gen. Patton are in their graves right now spinning in their graves. They don't believe what they're seeing."
The authors of the strongly worded letter include Michael Chertoff, the second director of Homeland Security under George W. Bush; Robert Kagan, a leader of the neoconservative movement and a member of the Council on Foreign Relations; Eric Edelman, former Under Secretary of Defense Policy during the Bush 41 administration and U.S. Ambassador to Turkey; and dozens of other former Republican presidential administration officials and conservative think tank members.
The letter was organized by Dr. Eliot A. Cohen, a counselor of the State Department from 2007-2008, and Bryan McGrath, the managing director of a defense consultancy.
"We have disagreed with one another on many issues...but we are united in our opposition to a Donald Trump presidency," they wrote in the letter, listing a series of Trump's positions they described as "core objections."
"His vision of of American influence and power in the world is wildly inconsistent and unmoored in principle," the signees wrote. "He swings from isolationism to military adventurism within the space of one sentence."
They also criticized Trump's controversial call for a temporary ban on Muslim entry into the U.S.
"His hateful, anti-Muslim rhetoric undercuts the seriousness of combating Islamic radicalism by alienating partners in the Islamic world making significant contributions to the effort. Furthermore, it endangers the safety and Constitutionally guaranteed freedoms of American Muslims," they wrote.
And the authors struck at the core of Trump's presidential pitch, dismissing his business experience.
"His equation of business acumen with foreign policy experience is false. Not all lethal conflicts can be resolved as a real estate deal might, and there is no recourse to bankruptcy court in international affairs," they wrote.
Additionally, they blasted Trump's "embrace of the expansive use of torture," charged him with "inflam(ing) unhelpful passions" in the immigration debate, and accused him of holding "the sentiment of a racketeer" regarding the U.S.'s relationship with its military allies.
The signees close the letter, "As committed and loyal Republicans, we are unable to support a party ticket with Mr. Trump at its head. We commit ourselves to working energetically to prevent the election of someone so utterly unfitted to the office."
The searing letter from the members of the conservative foreign policy establishment comes amid a frantic effort by some Republican Party leaders to deny Trump the GOP presidential nomination, after Trump's sweeping victories in the Super Tuesday contests this week bought him closer to securing the nod.