In an interview with Fox News on Thursday, Trump attacked the US State Department for not supporting his agenda.
"The one that matters is me," Trump said. "I'm the only one that matters because, when it comes to it, that's what the policy is going to be,” Trump said.
The US president also said he is “not happy” that some State Department officials are not supporting his agenda.
Asked if he planned to keep Tillerson on board for the rest of his term, Trump said, "Well, we’ll see. I don’t know."
Tensions between Trump and Tillerson resurfaced last month amid reports that Tillerson had called Trump a "moron" and had considered resigning over the summer.
Trump is heading to Asia on a 11-day trip with Tillerson following months of conflict between the two.
It will be his first official visit to Asia as president, and it will mark his longest continuous trip during his time in office.
Tensions between Tillerson and Trump have been simmering for months, sometimes visibly as the two have publicly diverged on some of the administration's most crucial foreign policy challenges, including Iran and North Korea.
FBI director James, Comey, White House press secretary Sean Spicer, White House chief of staff Reince Priebus and national security adviser Michael Flynn are among the senior officials forced from their roles by the Republican president early in his term.
Richard Haas, president of the Council of Foreign Relations, said Trump's comments spelled trouble not just for the current secretary but for overall American foreign policy.
"It's not just about Rex Tillerson, it's about who comes after Rex Tillerson. If the president is not determined to make sure his secretary of state will succeed, the secretary of state can't succeed," Haass told CBS News on Friday.