The fate of President-elect Donald Trump’s selection for his administration’s Secretary of State hinges in the vote of Florida Sen. Marco Rubio.

The Wall Street Journal reported that three Republican senators have expressed concern over Rex Tillerson, the former CEO of Exxon Mobil. Rubio is reportedly undecided on his vote and said he will not discuss the matter until he comes to a decision.

“We’re just going to continue to go through the process,” he said, according to the report. “And we’ll make a decision soon.

Tillerson and Rubio clashed during a pair of contentious exchanges Wednesday, with an incredulous Rubio pressing the prospective diplomat to brand Russian President Vladimir Putin a "war criminal" and Tillerson coolly blunting Rubio's broadsides by explaining his more deliberative vision.

The other Republicans concerned about Tillerson are Sens. Lindsey Graham and John McCain.

During the tense back-and-forths at the Senate Foreign Relations Committee confirmation hearing, Rubio, R-Fla., cross-examined Tillerson on policy regarding Russia, Cuba, Saudi Arabia and the Philippines. At the end of Rubio's second questioning period, Tillerson sought to allay any concerns the aggressive Rubio may have had.

"There seems to be some misunderstanding that I see the world through a different lens, and I do not," Tillerson said. "...But I'm also clear-eyed and realistic about dealing with cultures."

Tillerson's statement followed a heated initial session during which the ExxonMobil CEO refused to specifically call Putin a "war criminal."

"I find it discouraging your ability to cite that, which I think is globally accepted," Rubio said.