"It was an honor to have been considered for secretary of state of our great country. My discussions with President-elect Trump have been both enjoyable and enlightening. I have very high hopes that the new administration will lead the nation to greater strength, prosperity and peace," he said in Facebook post
Trump placed a call to Romney to tell him he would not be the pick, according to two sources familiar with the transition.
The call put to an end the long-running -- and very public -- courtship between two men who were at some points diametrically opposed, and at others harshly critical, of one another during the 2016 campaign.
But Romney, the 2012 GOP nominee, found himself in the running to be Trump's top diplomat despite those clashes, bolstered by multiple lengthy one-on-one meetings with the President-elect who publicly extolled the interactions.
Still, the opposition to Romney was fierce inside Trump's team -- something that spilled out publicly when Kellyanne Conway, Trump's former campaign manager and still close senior adviser made clear his criticism during the campaign should be considered a bridge too far.
While sources did not identify that as the reason Romney wasn't selected, Trump has chosen to move in a different direction, according to sources, and the call was made to Romney out of respect for his willingness to go the process and an appreciation for the perspective he brought to the table.
All signs point to Exxon Mobil CEO Rex Tillerson as Trump's final selection
for the position, sources told CNN, which Trump tweeted Monday night would be announced Tuesday morning.
"He did something I tried to do and was unsuccessful in accomplishing. He won the general election. And he continues with a message of inclusion and bringing people together and his vision is something which obviously connected with the American people in a very powerful way," Romney had told reporters after he dined with Trump at the ritzy Jean Georges in New York City.
The fight between Romney, the Republican Party's 2012 nominee, and Trump was nasty and personal.
After Romney said he didn't expect Trump to win the GOP nomination and called some of the real estate mogul's past comments "childish in some respects," Trump tweeted: ".@MittRomney can only speak negatively about my presidential chances because I have been openly hard on his terrible "choke" loss to Obama!"
Trump fired back, saying that he could have forced Romney to his knees in 2012 when Romney sought his endorsement.
"He was begging for my endorsement. I could have said, 'Mitt, drop to your knees' -- he would have dropped to his knees," Trump said.