"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.