(CNN) In one of his first tweets of the new year, President Donald Trump attacked retired four-star Army Gen. Stanley McChrystal after he criticized the President on Sunday.

The commander in chief's name-calling comes after McChrystal said during an interview Sunday that Trump was dishonest and immoral.

"I don't think he tells the truth," McChrystal told ABC's Martha Raddatz on "This Week." When asked if he thought Trump was immoral, McChrystal responded, "I think he is."

"What I would ask every American to do is, again, stand in front of that mirror and say, what are we about?" McChrystal continued. "Am I really willing to throw away or ignore some of the things that people do that are pretty unacceptable normally just because they accomplish certain other things that we might like. If we want to be governed by someone we wouldn't do a business deal with because their background is so shady, if we're willing to do that then that's in conflict with who I think we are."

"And so I think it's necessary in those times to take a stand," he said.

McChrystal also criticized Trump in November for his attacks on retired Adm. William McRaven, the leader of the Navy Seal unit that killed Osama bin Laden in 2011, who also has leveled sharp criticism at the President. Trump called the four-star admiral "a Hillary Clinton backer and an Obama backer" and said it would "have been nice if we got Osama bin Laden a lot sooner than that."

"The President is simply wrong," McChrystal told CNN's Jim Sciutto on "Newsroom." "He's uninformed, and he is pushing an idea that I think is not helpful. But I really think it's symptomatic of the crisis in leadership that we have in the nation today."

McChrystal wrote in a November column for CNN that "America is facing a leadership crisis," calling Trump "just the most bombastic example of this phenomenon, which has been playing out for decades."

McRaven responded to Trump's attack on McChrystal with a statement to CNN on Tuesday.

"Stan McChrystal is one of the great generals of this generation and the finest officer I ever served with," McRaven said. "He is a deep strategic thinker, tactically brilliant, with unparalleled personal courage. His leadership of special operations forces in Iraq and Afghanistan unquestionably saved the lives of thousands of American and allied troops, as well as countless civilians. No general I know has given more in the service of this country."

In his Sunday interview, McChrystal also reacted to James Mattis' resignation from the Trump administration as secretary of defense earlier this month. Mattis wrote in his resignation letter that Trump had the right to have a defense secretary whose views "better aligned" with the President's.

"If we have someone who is as selfless and as committed as Jim Mattis, resigns his position walking away from all the responsibility he feels for every service member in our forces, and he does so in a public way like that, we ought to stop and say, okay, why did he do it?" McChrystal said. "We ought to ask what kind of commander in chief he had that Jim Mattis, that the good Marine, felt he had to walk away."

McChrystal led US forces in Afghanistan under President Barack Obama, but resigned in 2010 over comments he and his top officers made in a Rolling Stone article that belittled other administration officials, including Vice President Joe Biden. Obama replaced him with Army Gen. David Petraeus.