U.S. Ambassador to Panama John Feeley, a career diplomat and former marine corps helicopter pilot, has resigned, saying he no longer felt able to serve President Donald Trump.

Feeley's departure had been communicated to State Department officials on Dec. 27 and was not a response to Trump's alleged use of the word "sh-thole" to describe Haiti and African countries at a meeting on Thursday, U.S. officials said.

Trump denies using the term.