Rubio indicated that he might not support Tillerson due to the Exxon CEO's ties to Russia and the country's president, Vladimir Putin.
"While Rex Tillerson is a respected businessman, I have serious concerns about his nomination," Rubio said in a Tuesday morning statement. "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. I look forward to learning more about his record and his views. I will do my part to ensure he receives a full and fair but also thorough hearing before the Senate Foreign Relations Committee."
Rubio's statement followed a tweet over the weekend referencing Putin.
Being a "friend of Vladimir" is not an attribute I am hoping for from a #SecretaryOfState - MR
— Marco Rubio (@marcorubio) December 11, 2016
Tillerson has the support of several prominent conservatives. Both former Defense Secretary Bob Gates and former Secretary of State Condoleezza Rice reportedly recommended Tillerson to the Trump team. Both now work for consulting firm that has Exxon as a client.
Sen. Lindsey Graham (R-SC) and Sen. John McCain (R-AZ) have also both signaled they're considering opposing Tillerson over his Russia ties, but Tillerson opponents would need more than two Republicans to vote against Tillerson in order to block his confirmation.