United States Ambassador to Panama John Feeley has resigned from his post, citing irreconcilable differences with the Trump administration, Reuters reported on Friday.

Feeley, a former Marine Corps helicopter pilot and a Latin America specialist, said that he felt that he was no longer able to serve under United States President Donald Trump. “As a junior foreign service officer, I signed an oath to serve faithfully the president and his administration in an apolitical fashion, even when I might not agree with certain policies,” Feeley said, according to an excerpt of a resignation letter read to Reuters on Friday.

He added: “My instructors made clear that if I believed I could not do that, I would be honor bound to resign. That time has come.” Feeley will step down on March 9.

Feeley had told State Department officials about stepping down on December 27, 2017, and so, it is not a direct response to Trump’s alleged use of the word “shithole” to describe certain nations, officials said.

Trump had reportedly used the word to refer to third-world nations from Africa, along with Haiti and El Salvador, when senators in his office were discussing means to protect immigrants in the United States. Trump interrupted the meeting and said, “Why are we having all these people from shithole countries come here?” Trump later denied using the word.