Washington: Daniel Kammen, a renewable energy expert appointed last year as a science envoy to the State Department, resigned on Wednesday, citing President Donald Trump's response to the violence in Charlottesville, Virginia, as the final straw that led to his departure.

In a resignation letter posted to Twitter, Kammen wrote that Trump's remarks about the racial violence in Virginia had attacked "core values of the United States" and that it would have "domestic and international ramifications."

However, his most biting message may have come in the form of a hidden acrostic; the first letter of each paragraph spelled out "I-M-P-E-A-C-H."

Demonstrations by white supremacist groups on August 12 turned deadly after a neo-Nazi ploughed a car into a crowd, killing one counterprotester and injuring at least 19 other people in Charlottesville. Two police officers were also killed when their helicopter crashed.