Former New York City Mayor Rudy Giuliani slammed the Obama administration this morning on "Fox and Friends" for releasing five Yemeni terror suspects from Guantanamo Bay. 

The five, who all have ties to al Qaeda, were transferred to Estonia and Oman. 

"You've got to be out of your mind to let killers go, at a time when people are being attacked and killed by Islamic terrorists," Giuliani said. "What is going on inside the White House? This could be the craziest thing the President of the United States has ever did."

The prisoners had been held for more than 12 years at the prison. Since 2009, they have been cleared for release, but the U.S. didn't send the prisoners back to Yemen because the government is battling an Al Qaeda insurgency. 

Giuliani criticized Obama for releasing the terrorists who he believes are going to kill Americans.

"On the front page of the New York Post today, we have an almost-attack on the United States," Giuliani explained. "And he's releasing killers to kill Americans! When you take the oath of office, you vow to preserve, protect, and defend the United States. Not let killers go who are going to kill Americans."

When asked why he thinks the president is releasing Guantanamo Bay detainees, Giuliani replied that he thinks the president is in a state of denial.

"I really now believe he's in a state of complete denial about the idea that we are at war," he shared. "He just won't accept it. Maybe it's arrogance, maybe it's his refusal to admit that he was wrong. They are at war with us. What do they have to prove to us after the bombing in France that they are at war with us?"

Giuliani added that "when you're at war, you don't let the warriors go free. We wouldn't have let the Nazis go free until the end of the war."

Watch the video above to hear more of the discussion, including Giuliani's thoughts on the 2016 presidential field.