Washington (CNN) The outgoing US ambassador to Panama issued a scathing critique of President Donald Trump and his foreign policies in an op-ed, saying that a betrayal of "the traditional core values of the United States" led to his resignation.

"I resigned because the traditional core values of the United States, as manifested in the President's National Security Strategy and his foreign policies, have been warped and betrayed," John Feeley, whose resignation takes effect Friday, wrote in a Washington Post op-ed.

Feeley said that impetus for his resignation came from Trump's failure to strongly condemn white supremacists for the violence in Charlottesville, Virginia, last summer that left one dead.

"(It) made me realize that my values were not his values," he wrote.

Feeley blasted a number of Trump's policy initiatives, including his proposed travel ban and southern border wall, his elimination of the Deferred Action for Childhood Arrivals program, his withdrawal of the US from the Paris climate deal and the Trans-Pacific Partnership, as "making the United States weaker and less prosperous."

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