A senior aide to Republican US President Donald Trump on Saturday apologized for promoting a racially-charged video on her Twitter feed.Mercedes Schlapp, a senior Trump national spokeswoman, said she "deeply apologized" for retweeting a video of a chainsaw wielding man in Texas shouting at anti-racist protesters, in which he used a racial slur. "I retweeted without watching the full video. I deleted the tweet. I would never knowingly promote the use of that word," Schlapp said in an email to Reuters.Schlapp's apology comes as the US is convulsed by protests after the police killing in Minnesota last month of a black man, George Floyd, by a white police officer, who knelt on his neck for nearly nine minutes. That officer has been charged with second degree murder and three fellow officers have been charged in abetting Floyd's death.