WASHINGTON, June 7 (CGTN) - Colin Powell, who served as America's top military officer and top diplomat under Republican presidents, said Sunday he will vote for Democrat Joe Biden, accusing Donald Trump of drifting from the U.S. constitution and Republicans of failing to hold him accountable.

In a scathing indictment of Trump on CNN, Powell denounced the U.S. president as a danger to democracy whose lies and insults have diminished America in the eyes of the world.

"We have a constitution. We have to follow that constitution. And the president's drifted away from it," Powell said.

A retired four-star army general, Powell was the latest in a series of retired top military officers to publicly criticize Trump's handling of the mass anti-racism protests that have swept the United States since the police killing of George Floyd, an unarmed black man, in Minneapolis on May 25.

A tipping point appeared to have been reached last week among the normally reticent retired officers when Trump threatened to use the active duty military to quell protests in U.S. cities, setting off a confrontation with the Pentagon leadership.

Among those who broke their silence was Trump's former defense secretary, Jim Mattis, a retired Marine general who accused the president of deliberately setting Americans against each other and making "a mockery of our Constitution."

Powell's comments carried particular force as the nation's first and so far only African American chairman of the Joint Chiefs and the country's first black secretary of state, serving under Republican presidents George H.W. Bush and George Bush respectively.

Powell blasted Republican senators for not standing up to Trump.

"We are in a turning point," he said.

"He lies about things. And he gets away with it because people will not hold him accountable," he said, referring to Trump.

Powell also rebuked Trump for offending "just about everyone in the world."

"We're down on NATO. We're cutting more troops out of Germany. We have done away with our contributions to the World Health Organization. We're not happy with the United Nations.

"And just about everywhere you go, you'll find some kind of disdain for American foreign policy that is not in our interests," he said.