During Wednesday's confirmation hearings, Rubio grilled Tillerson on human rights, and at one point, Tillerson balked at calling Russian President Vladimir Putin a "war criminal."
"These questions were designed for a specific reason, and that is, if we're going to have moral clarity in our foreign policy we need to be clear. And I don't want to see us move towards a foreign policy in which human rights matter when nothing else matters, when something more important isn't standing in the way," Rubio told reporters after the hearing.
Rubio added that he intended to go back and look through the Tillerson's answers before making the decision whether to support him.
"I have to make sure that I am 100 percent behind whatever decision that I make, because once I make it, it isn't going to change," Rubio said.