Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE didn’t thank President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE in a Tuesday press conference responding to the president announcing his firing on Twitter.

Tillerson praised State Department officials and Defense Department staff for their work during his tenure, while also thanking members of the military and the American people.

But Tillerson did not mention Trump by name, only referring once to the president.

“I received a call today from the president of the United States a little after noontime from Air Force One, and I’ve also spoken to White House chief of staff [John] Kelly to ensure we have clarity about the days ahead,” Tillerson said. "What is most important is to ensure an orderly and smooth transition during a time that the country continues to face significant policy and national security challenges."

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Tillerson also took a parting shot at Russia, saying “much work remains to respond to the troubling behavior and actions on the part of the Russian government.”

“Russia must assess carefully as to how its actions are in the best interests of the Russian people and of the world more broadly,” he added. “Continuing on their current trajectory is likely to lead to greater isolation on their part, a situation which is not in anyone’s interest.”

Trump has caught flak for his muted criticisms of Moscow and Russian President Vladimir Putin after the U.S. intelligence community determined Russia sought to interfere in the 2016 presidential election in an effort to help Trump win.

The Trump administration has not implemented sanctions against Russia that overwhelmingly passed both chambers of Congress last year.

Trump tweeted Tuesday morning that he had removed Tillerson as the nation's top diplomat and replaced him with CIA Director Mike Pompeo Michael (Mike) Richard PompeoUS reimposes UN sanctions on Iran amid increasing tensions Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Trump steps up Iran fight in final election stretch MORE, a surprise announcement.

Trump is nominating Gina Haspel, Pompeo’s current deputy, to lead the CIA.

Trump told reporters Tuesday morning that he made the decision “by myself,” signaling he did not speak with Tillerson before firing him.

“I actually got along great with Rex, but really, it was a different mindset,” Trump said from the White House.

Tillerson did not take questions from reporters after making his statement on Tuesday afternoon at the State Department.

The former longtime Exxon Mobil chief had an often tense relationship with Trump, refusing to deny reports that he called the president a "moron" last year.

Tillerson said his term as the nation's top diplomat will end at midnight on March 31. Until then, Tillerson is delegating his responsibilities to Deputy Secretary of State John Sullivan.