One of the U.S. State Department's science envoys publicly resigned on Wednesday, the latest in a wave of defections over President Donald Trump's response to a white nationalist rally in Charlottesville, Virginia.

Daniel Kammen, a professor at the University of California, Berkeley, said in a letter posted on his Twitter account that Trump had failed to condemn white supremacists and neo-Nazis, part of "a broader pattern of behavior that enables sexism and racism, and disregards the welfare of all Americans, the global community and the planet."

Trump told reporters last week that "both sides" were to blame for the violence between white supremacists and counterprotesters in Virginia on Aug. 12, and said there were "very fine people" among those who participated in the white nationalist rally.