Sen. Marco Rubio fired a warning shot at secretary of state nominee Rex Tillerson, saying he has “serious concerns” that the Exxon Mobil CEO might have conflicts of interest and a lack of “moral clarity” needed in the nation’s top diplomat.

“While Rex Tillerson is a respected businessman, I have serious concerns about his nomination,” the Florida Republican said Tuesday morning. “The next secretary of state must be someone who views the world with moral clarity, is free of potential conflicts of interest, has a clear sense of America’s interests, and will be a forceful advocate for America’s foreign policy goals to the president, within the administration, and on the world stage.”