Washington (CNN) Joseph Yun, the former State Department Special Representative for North Korea, confirmed Monday that he signed an agreement to pay North Korea $2 million for the release of American student Otto Warmbier in 2017.

In an interview with CNN's Jim Sciutto, Yun said that he did so with the approval of then-Secretary of State Rex Tillerson and that it was his understanding President Donald Trump had also signed off on the decision.

"As soon as North Korea side told me that this bill for $2 million would have to be paid ... I contacted my boss then-Secretary of State Rex Tillerson," Yun said, noting that Tillerson "got back to me very quickly thereafter to say yes, go ahead and sign."

The former US Special Representative added that it was his understanding the decision had been approved by Trump himself.

"That was my understanding. I never asked him, but that was my understanding," he said when asked if he believed Tillerson had Trump's approval.

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