Russian President Vladimir Putin thinks that Republican presidential nominee Donald Trump is an "unwitting agent" of his federation, a former top American spy master said on Sunday.

"In Putin’s mind, I have no doubt that Putin thinks that he (Trump) is an unwitting agent of the Russian Federation, although Putin would never say that," former CIA acting director Michael Morell told ABC News in an interview.

Early this week, Morell had endorsed Hillary Clinton, the Democratic presidential nominee, and had said Trump is not fit to lead the country.

He also questioned Trump’s relationship with Putin, which the Republican nominee has denied.

"Look at it from Putin’s perspective, right. He’s a trained intelligence officer, worked for the KGB, very talented, manipulated people much smarter than Donald Trump.

He played this perfectly, right. He saw that Donald Trump wanted to be complimented," Morrell said.

"He complimented him. That led Donald Trump to then compliment Vladimir Putin and to defend Vladimir Putin’s actions in a number of places around the world," he said.

"Donald Trump didn’t even understand that Putin was playing him. From Trump’s perspective, he simply heard Putin compliment him. He then responded by complimenting him.

He never thought that he might be played," Morrell said.

Morrell, who worked with Clinton for four years said that the former secretary of state never misused the classified information that he gave to her.

"I worked with her for four years very closely when she was secretary of state and I was at the CIA. I personally provided her some of the most sensitive information that the Central Intelligence Agency has. She never misused it. She always protected it," he said.

"I would trust her with the crown jewels of the United States government. And, more importantly, I would trust her with the future security of the country and the future security of my kid," he stressed.

Responding to a question, Morrell said he is also concerned about the prospects of ISIS supporters entering the country in the garb of refugees.

But a blanket ban on entry of Muslims in the country is not the solution, he said.

"So I’m concerned, too, about ISIS’ ability, right, to infiltrate people. But we have got some very effective, robust processes for vetting people. We brought in thousands of Iraqi refugees after the Iraq War. Not a single one ever turned out to be a terrorist because the vetting was so good," he said.

"So I want the vetting to be solid. But I also want to bring these people in because not bringing them in sends a message to the Muslim world and plays into the ISIS narrative and the al-Qaeda narrative that this is a war between religions. And we can’t have that," Morrell said.