US President Donald Trump has called the congressional impeachment investigation that may seek to remove him from office "a lynching", APA reports citing BBC.
Mr Trump condemned the inquiry in a tweet as "without due process or fairness or any legal rights".
But Democrats were outraged at the president for invoking such a grim and racist chapter from US history.
Lynching refers to historic extrajudicial executions by white mobs mainly against black people.
White House spokesman Hogan Gidley told reporters on Tuesday that Mr Trump did not mean to be racially insensitive.
"The president has used many words, all types of language, to talk about the way the media has treated him," the deputy press secretary said.
He added: "The president wasn't trying to compare himself to the horrific history in this country at all."