Sen. Lindsey Graham questioned whether former National Security Adviser Michael Flynn was directed to talk about the United States' sanctions on Russia by someone on Trump's transition team, Talking Points Memo reported.

"I want to know, did Gen. Flynn do this by himself or was he directed by somebody to do it?" Graham told CNN's Kate Bolduan on "At This Hour."

Flynn resigned late Monday from his position, a few days after The Washington Post reported he had misled Vice President Mike Pence about his conversation with the Russian ambassador. Pence publicly claimed Flynn had not spoken about the sanctions, which were issued by Barack Obama after intelligence agencies found evidence Russia interfered in the 2016 presidential election.

Flynn, in a statement, said he had given "incomplete information" and he had spoken about the sanctions with Sergey I. Kislyak in late December.

Graham, who served in Afghanistan with Flynn, said he had "a hard time" believing Flynn would "get on the phone with an ambassador and say, don't worry, we'll revisit this when we get to the president in terms of executive sanctions, without some understanding that the administration would be sympathetic to the idea."

"I may be wrong. Maybe he did this in a rogue fashion. Maybe Gen. Flynn went rogue, but that's . . . I don't know. He's a pretty strong-willed fellow," Graham continued.

"But I think most Americans have a right to know whether this was a Gen. Flynn rogue maneuver or was he basically speaking for somebody else in the White House?"